Investigators are examining whether foggy conditions and technical glitches at a San Diego airport that cut off lights meant to guide pilots may have played a role in a fatal plane crash.
A Cessna 550 crashed early Thursday into a residential neighbourhood, burning cars and destroying at least one home.
Authorities say all six aboard are presumed dead, including a former drummer for the rock band The Devil Wears Prada and a high-profile music agent.
The National Transportation Safety Board is examining a mix of clues and said the aircraft did not have a flight data recorder, which would have provided more information. Officials have not yet determined what factors led to the crash.
In a news conference on Friday, NTSB investigator Dan Baker said the agency is receiving help from the FBI as it works to collect and preserve evidence from the scene.
He said investigators have found the plane had struck high-tension power lines before crashing into homes in the Murphy Canyon neighbourhood, about two miles from the Montgomery Field Airport - where the plane was heading.
The airport, a small regional airport with three runways, was experiencing two separate issues at the time of the crash, Mr Baker said. The Automated Surface Observing Station, which provides weather data to pilots, was "inoperative at the time of the accident due to an unrelated power surge".
At the time, foggy conditions had been reported throughout the area.
Mr Baker attributed the outage to "some sort of technical glitch", but cautioned that it is unclear whether this contributed to the crash since not all airports are equipped with this system.
The airport also had filed a notice to pilots called a Notam, informing them that one of the runways had experienced an issue with the lighting system that guides landing planes.
The pilot of the downed plane had been aiming for that runway when the crash occurred, Mr Baker said.
The pilot did not report any issues to air control and never declared an emergency, Mr Baker said.
The Cessna was not equipped with a flight data recorder, and officials are investigating whether it may have had a cockpit voice recorder onboard.
The crash happened around 3:45 local time (10:45 GMT) and about 100 people had to be evacuated from the neighbourhood, which is just northeast of the city of San Diego.
Eight people on the ground were injured, including one who was taken to hospital.
A preliminary report from the NTSB is expected to be released within 30 days, with a final report in the next 12 to 24 months.
Victims include Sum 41 agent and drummer
The names of four of the six people aboard the flight when it crashed have thus far been released.
Emma Huke, 25, and Kendall Fortner, 24, were named as being on the plane by their employer, Sound Talent Group.
Fortner "was the life of the party and lit up any room she entered," the company said in a statement on Friday.
Huke was "a beautiful soul who brought joy and a light to everyone in her presence".
The company had earlier confirmed the death of its co-founder, prominent music agent Dave Shapiro. Shapiro had worked with rock groups including Sum 41, Story of the Year, Parkway Drive and singer Vanessa Carlton.
He was also an avid pilot and a certified flight instructor with 15 years of experience, according to his aviation company Velocity Aviation.
Former The Devil Wears Prada drummer Daniel Williams was also killed in the crash, members of the group confirmed in tributes posted online.
In the hours before the crash, he posted images on Instagram of himself and Shapiro sitting in the cockpit of the plane, according to the San Diego Union-Tribune.
Williams was a founding member of The Devil Wears Prada and part of the Christian metal band for more than 10 years before parting ways in 2016.
The band posted a series of photos of Williams on Instagram, showing him with drumsticks, flying in an aircraft and various moments with fellow bandmates.
"no words. We owe you everything," the post reads. "Love you forever."
