California seeks solution as LA chemical tank heats up

Firefighters trying to keep a tank of hazardous chemicals in California from exploding or leaking brought in outside experts to help prevent a catastrophe, the incident commander said, as some nearby shelters ran out of space for evacuees.

Evacuation orders remained in place for an area covering tens of thousands of people in the Garden Grove suburb of Los Angeles.

California Governor Gavin Newsom declared a state of emergency for Orange County, and his office pleaded for residents to follow evacuation orders.

"We have brought in subject matter experts from all across the state to think completely outside the box, and we had some really good productive conversations today," Craig Covey, division chief of the Orange County Fire Authority, said in a video posted on social media.

He did not elaborate on possible solutions.

Shift to offensive from defensive as risk grows

Evacuation shelters were reported at full capacity in Anaheim, Fountain Valley, La Palma and Huntington Beach.

Crews had gone back into the danger zone overnight after drone readings on Friday suggested water sprayed on the tanks was helping stabilise the situation, Mr Covey said earlier.

But when crews reached the tank's gauge, they found the internal temperature was 32C, up from 25C when responders had pulled back.

The temperature was increasing by about one degree an hour, he said. "That's the bad news."

Officials have warned since Friday that the tank, which contains methyl methacrylate, a flammable chemical used in plastics and manufacturing, could rupture and spill up to 26,500 litres of toxic material or explode and endanger nearby tanks.

Mr Covey said firefighters were exploring whether a heavy flow of cooling water might slow the curing process inside the tank enough to reduce pressure and prevent an explosion.

"Letting this thing just fail and blow up is unacceptable to us," he said.

The incident began on Thursday at the GKN Aerospace facility in Garden Grove, a city of about 172,000 people roughly 50 km south of Los Angeles.

The site specialises in the manufacturing and testing of windows and canopies for commercial and military aircraft, according to its website.

GKN said it was working with "all relevant experts" to solve the problem.

"We sincerely apologise for the significant disruption to the many local residents and businesses who have had to be evacuated," a GKN spokesperson said in a statement.

Mr Covey said crews shifted from a "defensive" stance to an "offensive" operation overnight with help from chemists from the manufacturer's emergency response team.

The goal was to neutralise a nearby 15,000-gallon tank and reduce its explosive potential if the smaller tank failed.

"We did put people in harm's way last night," Mr Covey said.

Health officials have said they were concerned that vapour from the chemical could cause severe respiratory problems with prolonged exposure.

Air-quality monitors had not detected vapour as of the latest health update cited by officials.

"You are safe as long as you are out of the zone that was determined to be an evacuation zone," Dr Regina Chinsio-Kwong of the Orange County Health Care Agency said on Friday.

Mr Covey said crews were also preparing for a possible spill by looking for ways to dike, dam and divert the liquid into a holding area at the commercial site, rather than allow it to reach storm drains, river channels or the ocean.

"We are not giving up," he added.