Los Angeles Fire Department officials investigating Wednesday's fatal explosion in Westchester are looking into several potential causes, including the presence of gas and the possibility that a firefighter's power saw ignited the blast that killed one firefighter and critically injured another, authorities said Thursday.
"Was it an electrical issue, was it a methane issue, was it something that sparked? All that takes looking at evidence to determine," said Los Angeles Fire Capt. Armando Hogan. "We can't rule anything out yet, and we have to rule out the other possible causes before we can say definitively where the problem lies."
While fire investigators remained on the scene late Thursday, city firefighters and friends mourned the death of firefighter Brent A. Lovrien, 35, and sent get-well cards to Engineer Anthony J. Guzman, 48, who was seriously injured in the blast.
Security guards from the Hilton Los Angeles Airport Hotel across the street from Fire Station 95 dropped off two flower arrangements addressed to Guzman and the firefighters as a U.S. flag outside flew at half staff.
Graham Taylor, the hotel's director of safety and security, said the group knew the two firefighters, who often responded to calls at the hotel.
"We're like a big extended family," Taylor said.
Investigators have talked by phone with the state fire marshal and governor's offices, and the governor sent a representative to Los Angeles. A forensic investigator is also coming from Maryland.
As investigators searched for the cause of the blast Thursday, witnesses recounted hearing three distinct explosions, the last one being the fatal one, shortly before 2 p.m. Wednesday.
Charles Mordi said he watched as firefighters responded to a report of smoke coming from manhole covers. He then watched firefighters struggling to open the door to an electrical vault next to the Water and Power Community Credit Union in the 8800 block of Sepulveda Boulevard.
Mordi, who owns an employment testing business above the credit union, said he called 911 after hearing an explosion up the street. He also saw smoke coming from the utility room.
Within minutes of his call, he said, a firefighter arrived and tried to open the door to the utility room, which was locked. Moments later, an engine arrived with the two firefighters. They also tried without success to open the door. One went to the truck and returned with a yellow circular saw.
"As soon as he turned it on and put it by the door, that was when the explosion occurred," Mordi said. "It threw him almost six feet from where he was standing."
Lovrien, a 10-year veteran of the department, was injured in the blast and died after he was taken to Centinela Freeman Regional Medical Center. Guzman, an 18-year veteran, was taken to UCLA Medical Center in Westwood with multiple fractures and facial trauma, fire officials said. He remained in serious but stable condition Thursday after surgery.
Employees of a Quiznos sandwich shop reported that they smelled gas shortly before the incident, according to officials with the L.A. County Department of Water and Power. On Thursday, fire investigators appeared to be focusing their attention on an electrical panel housed in a utility room between the Quiznos and the credit union.
Nick Patsaouras, president of the DWP commission, said Fire Department officials told his agency that any spark given off by the saw -- used by firefighters trying to enter the vault containing electrical meters for nearby businesses -- could have ignited the blast if methane or another gas was already in the air.
"We were told that the saw could have been the problem," Patsaouras said.
On Thursday, a yellow saw similar to the one Mordi described was still in front of the credit union as investigators -- including federal law enforcement officials and representatives from private gas and oil companies -- examined the scene. Yellow caution tape still surrounded much of the block.
About 400 customers were still without power Thursday night, DWP officials said.
A civilian was also injured by the explosion but was treated and released at the scene, fire officials said.
Optometrist Kent Ashcraft, who was working in a nearby office, said he heard two blasts. The second was "like a sonic boom. The walls shook," he said. Cheryl Jackson, an optician who works with Ashcraft, said she heard three explosions.
"I had never heard anything that loud," she said of the final blast.
molly.hennessy-fiske @latimes.com, firstname.lastname@example.org; andrew.blankstein @latimes.com
Times staff writer Bob Pool contributed to this report.