The dramatic Sunday blaze that destroyed portions of the Universal Studios Hollywood back lot was accidentally touched off by company employees using a blowtorch to heat asphalt roofing shingles, authorities said.
Los Angeles County fire officials said two workers and a supervisor were putting up shingles in an alley on the New York Street set. They finished at 3 a.m., spent an hour watching for any sign of fire, then took a break.
At 4:43 a.m., just as the crew was returning, a security guard saw flames and reported the fire.
The studio's theme park and adjacent CityWalk reopened Monday as the Los Angeles County Fire Department launched what Fire Chief P. Michael Freeman promised would be a "stem to stern" examination of the water pressure problems that hampered the attack on the three-alarm blaze, which destroyed back lot sets, a video library and the "King Kong" attraction.
"The big question right now is trying to compare water available on site, off site and in the system itself with the amount of fire that the first arriving units were confronted with," Freeman said.
When the first fire engine arrived from a station on the Universal grounds four minutes after the blaze was reported, the New York Street sets were already engulfed in flames, Freeman said.
"About the equivalent of a city block of fire" greeted the first firefighters, he said. Fire officials said Sunday that some firefighters could only get 10-foot sprays from their hoses, and county Supervisor Zev Yaroslavsky said water was coming out of hoses anemically.
It is unclear, Freeman said Monday, whether a heavy-duty sprinkler system installed after a 1990 back lot fire in the same area affected the water pressure. But commanders told Freeman that they had to draw water from studio ponds and run hoses to hydrants off the studio lot in the early stages of fighting the fire.
The Los Angeles Department of Water and Power supplies Universal with water from surrounding mains. Agency Public Affairs Director Joe Ramallo said the DWP system was supplying adequate water during the fire. But Universal, like many large commercial sites, operates and maintains its own water system once lines come on to its property.
"You're limited by the system in place on the grounds and if it's not sufficient, you can't do any more on our side," Ramallo said. "We did everything we could to increase pressure on our end, but we were very limited because it's a private system."
Freeman said that an interdepartmental inquiry into the fire would be completed by June 13.
He said investigators will also look into whether the back lot sets, which have burned before, could be made of less combustible materials. The wood and plastic fed 100-foot flames that quickly moved into the adjacent "King Kong" building and a video library containing thousands of copies of movies and TV shows.
The fire, which turned a two-block area of the back lot into smoldering ruins, was not fully extinguished until 10 p.m. Sunday. More than 400 firefighters from the county and surrounding cities fought the blaze, which pumped out a huge column of black smoke that drifted across the San Fernando Valley.
On Monday morning, 40 to 50 firefighters were still dousing hot spots and looking for embers.
The fire affected about 3 1/2 acres of the 391-acre park, Universal said, with damage estimated in the millions of dollars.
A Universal spokesman said the studio would replace the New York Street backdrops and an animatronic King Kong destroyed by the fire. Park officials plan to reroute the studio's popular tram ride around fire-damaged sets to areas untouched by the flames.
The park's 30 soundstages were not damaged by the fire, Universal said, and 10 scheduled productions were still filming Monday.
Freeman said that during the 1990 back lot fire, "water supply was a challenge" as well, but not to the same degree as Sunday.
After that fire, Universal installed a heavy-duty sprinkler system designed to drench the sets in case of fire. Firefighters reported seeing water flow Sunday, Freeman said, but were uncertain whether it was coming from the sprinklers or from burst pipes.
At a Monday afternoon news conference, Freeman said it was too soon to draw conclusions about the low water pressure.
"At this point it is premature to say that there was a weak link," he said. "It may be that the large size of the fire was the issue."
Universal Studios Hollywood representatives declined to comment about the water-pressure issues.
Universal Music Group, an unrelated company, leased space in one of the video library vaults for master copies of reel-to-reel audiotapes of music from the 1940s and 1950s, but all of the archive had been copied, much of it digitally, as the site was being phased out, a spokesman said Monday, "so in a sense nothing was lost."
Preliminary results of air tests at Universal Studios' smoky back lots Sunday found levels of benzene and other toxic contaminants six times or more above normal.
At those levels, firefighters and anyone else in the immediate vicinity of the blaze could have experienced respiratory irritation, South Coast Air Quality Management District spokesman Sam Atwood said. But Atwood added that the measurements were far below the limits for serious health effects from short-term exposure.
Times staff writers Janet Wilson and Robert Lopez contributed to this story.