Six people were killed when a small plane crashed and burst into flames in a field during the second of two landing attempts in fog at a Southern California airport, authorities said.

The crash of the Cessna C550 business jet occurred around 4:15 am on Saturday in Murrieta, about 80 miles (130 kilometres) southeast of Los Angeles, according to the Federal Aviation Administration. It took firefighters more than an hour to extinguish the flames, which had engulfed the plane and charred about an acre of vegetation just north of French Valley Airport, said the Riverside County Fire Department.

All six people on board died at the scene, the Riverside County Sheriff’s Office said in a statement. The victims were not immediately identified.

The plane, which had departed from Harry Reid International Airport in Las Vegas, crashed during its second approach to French Valley’s single runway, the National Transportation Safety Board said in a statement.

Max Trescott, a California flight instructor who hosts the Aviation News Talk podcast, said data from a plane tracking website showed poor visibility in the moments before the crash. Conditions were deteriorating minute-by-minute after the pilot aborted the first landing attempt and circled back for another try, he said.

“The weather did get worse during the time they were making their two approaches,” Trescott told the Los Angeles Times.

It wasn’t clear why the pilot attempted to land on the second approach.

Five NTSB investigators were expected at the crash site later Saturday, the agency said. A preliminary report was expected in about 15 days.

The FAA’s aircraft tracking database lists the jet as owned by Prestige Worldwide Flights LLC of Imperial, California. Officials with the company could not be reached for comment.

It was the second fatal crash this week at the small county-owned airport in Murrieta, a city with about 1,12,000 residents. A man was killed and three people were injured on July Fourth when a single-engine Cessna 172 crashed in a parking lot shortly after takeoff from French Valley.