By HANNAH FRY, RICHARD WINTON, LUKE MONEY, RUBEN VIVES, MATTHEW ORMSETH of the Los Angeles Times

Federal investigators on Monday began working to unravel the mystery of why a helicopter carrying Kobe Bryant, his 13-year-old daughter and seven other people slammed into the side of a hill in Calabasas.

Authorities said the investigation is now wide-ranging, including looking at the histories of the pilot, helicopter maintenance records and the foggy conditions, which pilots have said add a level of danger.

Firefighters responding to a 911 call at 9:47 a.m. Sunday found a debris field in steep terrain with a quarter-acre brush fire. Paramedics arriving by helicopter searched the area but found no survivors.

Bryant, who lived in Newport Beach and Los Angeles, was known to keep a chartered helicopter at Orange County’s John Wayne Airport.ADVERTISEMENT

A Sikorsky S-76 chopper, built in 1991, departed John Wayne at 9:06 a.m. Sunday, according to publicly available flight records. The chopper passed over Boyle Heights, near Dodger Stadium, and circled over Glendale during the flight. The National Transportation Safety Board database shows no prior incidents or accidents for the mid-size helicopter.

Kurt Deetz, a former pilot for Island Express Helicopters, told The Times he flew Bryant from 2014 to 2016. Nine times out of 10, he said, Bryant flew in “Two Echo X-ray” — the Sikorsky S-76B, tail No. N72EX, that went down Sunday morning. Bryant favored the model, which is preferred by celebrities for its comfortable interior and solid safety record, Deetz said.

When Bryant retired from the NBA in 2016, he flew out of downtown Los Angeles in the same helicopter, wrapped in a gray-and-black paint scheme with his Mamba emblem on the side, Deetz said.

Deetz suspects the crash was most likely caused by bad weather rather than engine or mechanical issues. “The likelihood of a catastrophic twin-engine failure on that aircraft — it just doesn’t happen,” he said.

Parts of Southern California were enveloped in thick fog as the helicopter made its way from Orange County to Los Angeles. During the flight, the pilot noted he was flying under “special visual flight rules,” which allows a pilot to fly in weather conditions worse than those allowed for standard visual flight rules, according to radio communications between the air tower and the aircraft. At some point during the flight, the pilot apparently requested “flight following,” a process in which controllers are in regular contact with an aircraft and can help them navigate.

The tower is heard telling the pilot the chopper is too low for flight following before the conversation ends. There did not appear to be a distress call.

A visual flight rules flight “is based on the principle of see and avoid.” When operation of an aircraft under visual flight rules isn’t safe, often because of inclement weather, a pilot can opt to fly under instrument flight rules. During this type of flight, the pilot navigates only by reference to the instruments in the aircraft cockpit, according to the FAA.

“[Pilots] fly VFR when and if weather conditions allow, although they can choose to fly on an IFR flight plan at any time,” said Ian Gregor, a spokesman for the FAA. “Also, it’s always up to the pilot to make the decision whether to fly VFR and to ensure the safety of the flight and adherence to federal aviation regulations.”

Bryant was scheduled to coach Sunday in a game against the Fresno Lady Heat at his Mamba Sports Academy in Thousand Oaks and was en route there when the helicopter crashed. The tournament, called the Mamba Cup, featured boys’ and girls’ travel teams from fourth through eighth grades. Bryant’s daughter Gianna, who attended Harbor Day School in Newport Beach, was scheduled to play.

The Federal Aviation Administration and National Transportation Safety Board are investigating the crash. The FBI is also assisting in the probe, which is standard practice. The helicopter was registered to Fillmore-based Island Express Holding Corp., according to the California secretary of state’s business database. The helicopter’s manufacturer, Sikorsky, said in a statement Sunday that it was cooperating with the investigation.

The National Transportation Safety Board dispatched a “go team,” a squad of investigators that responds to major accidents across the country, Sunday evening, said Christopher O’Neil, an agency spokesman. Leading the investigation is Jennifer Homendy, an NTSB member who oversaw the investigation of a fire aboard the dive boat Conception that killed 34 people off Santa Cruz Island in September.

“Our team will be looking at the history of the pilot…whatever crew was on board. We’ll be looking at maintenance records. At records of the owner and operator. And a number of other things as part of the investigation,” Homendy said.

On Monday morning, the L.A. County coroner’s special response team was working on a ridge above the crash site, continuing to remove the remains of the nine victims with the help of search and rescue team members.

Experts have said weather conditions and possible mechanical issues will likely be at the top of the list for investigators.

The fog was severe enough Sunday morning that the Los Angeles Police Department’s Air Support Division grounded its helicopters and didn’t fly until later in the afternoon, department spokesman Josh Rubenstein said.

“The weather situation did not meet our minimum standards for flying,” Rubenstein said. The fog “was enough that we were not flying.” LAPD’s flight minimums are 2 miles of visibility and an 800-foot cloud ceiling, he said.

The L.A. County Sheriff’s Department made a similar assessment about the fog and had no helicopters in the air Sunday morning “basically because of the weather,” L.A. County Sheriff Alex Villanueva said.

Witnesses said they heard a roar before the chopper slammed into the hillside Sunday morning.

Jerry Kocharian, 62, was standing outside the Church in the Canyon drinking coffee when he heard a helicopter flying unusually low and seeming to struggle.

“It wasn’t sounding right, and it was real low,” Kocharian said. “I saw it falling and spluttering. But it was hard to make out as it was so foggy.”

The helicopter vanished into the sheet of fog, then there was a boom and “a big fireball,” he said.

“No one could survive that.”

Scott Daehlin, 61, was taking a break from setting up sound for a service at Church in the Canyon, which is below the crash site, when he heard the helicopter overheard.

“Because of its proximity to the ground, I knew something was wrong. It was hovering real low, like they were searching to land. It was making a slow left turn. It was about 9:44 a.m., and then the impact happened. I heard a crunch. I don’t think it pancaked. I think it hit rotors first,” Daehlin said. “I immediately called 911.”

The pilot, identified as Ara Zobayan, and eight passengers — including Bryant and his daughter — were killed. Orange Coast College baseball coach John Altobelli, 56, his wife, Keri, and their daughter Alyssa, who played on the same club team as Gianna, also were killed. Christina Mauser, who was the top assistant coach of the Mamba girls’ basketball team, as well as a mother and daughter from Orange County, identified by family and friends as Sarah and Payton Chester, also died in the crash.

Officials say the recovery effort at the crash site is expected to take days.

As officials work to find answers about what went wrong during the flight, Southern Californians continue to mourn the death of an athlete who over the course of his 20-year career became one of the greatest shooting guards in the history of basketball.

In Newport Beach, where Bryant lived with his family for years, two young girls dressed in Lakers colors — purple and gold — dropped flowers off at a bench outside Harbor Day School, adding to a makeshift memorial that has sprouted over the last day. The Bryant family was active at the private school, where at least one of his daughters had attended.

Two bouquets propped up under the school’s entrance sign were left with letters, one addressed to “Gigi, Mr. Bryant and Mrs. Mauser, Forever in our Hearts” and the other “To Mr. Bryant, Gigi and Mrs. Mauser, Our 3 Angels.”

Maria Paun, 81, used her walker to deliver an assortment of pink flowers to the front of the school, depositing them on a bench. It was years ago, she said, that she sat with Bryant on a bench at the school when he was waiting to pick up one of his daughters and she was waiting for her granddaughter.

“He gave me a hug and he said, ‘I like your accent, Grandma,’ ” she said. “He was tall, and he was somebody and I’m nobody, but he bent down to give me a hug. And I never forget this hug.”

Paun said it was no accident that she wore a purple sweater Monday morning. She did so because “he liked the color.”

“It’s hard for me, and it’s hard for everyone,” she said, her voice cracking with emotion.

During a vigil Sunday night, Bryant’s fellow Newport Beach residents spoke of the athlete’s life outside of his storied NBA career. He was, first and foremost, a dedicated father whose love for his family was apparent to anyone who came across him, friends say. He was also the type of man whose fame never got in the way of his sharing a warm greeting at Starbucks or the grocery store.

Mario Nunes, 50, hung his Kobe Bryant jersey from one of the tables in front of the Pavilions grocery store on Newport Coast Drive, where Bryant was known to frequent, on Monday. Nunes, a job trainer with the Rehabilitation Institute of Southern California, said he used to see Bryant at the store every few weeks. Nunes was quick to whip out his phone to show some of the pictures he’d taken with Bryant over the years, including one he said was from shortly after the Lakers’ last championship in 2010.

“He was always cool with me,” he said. “He was always friendly. He signed a couple basketballs here and there.”

Michael Young, 40, said he also saw Bryant periodically during the three years he’s worked as a courtesy clerk at the grocery store. When he heard the news about Bryant’s death, Young said his first reaction was tears.

“He brought a lot of good energy … a lot of positive energy, a lot of good stuff for the community,” Nunes said.

Both Young and Nunes said the shock of seeing the superstar in the flesh never completely wore off, no matter how many times he came to the grocery store or made a run to the Starbucks in the same shopping complex.

“It’s like he’s still here,” Young said. “His spirit is all around us.”