Experts trying to prevent a tank of hazardous chemicals from exploding in Southern California found a “potential crack” in the container that might be reducing the pressure, a fire official said on Sunday.

Since Friday, officials have warned that the tank, which contains methyl methacrylate, a flammable chemical used in plastics and manufacturing, could rupture and spill up to 7,000 gallons (26,500 liters) of toxic material or explode and endanger other tanks on the GKN Aerospace site.

Evacuation orders were issued on Friday for an area in Garden Grove, a suburb roughly 30 miles (48 kilometers) south of Los Angeles. Tens of thousands of people are covered by the evacuation orders.

TJ McGovern, interim fire chief of the Orange County Fire Authority, said in a video message posted on social media that a team of specialists on Saturday night found “a potential crack in the tank, which could potentially be relieving some of the pressure in there.”

Discovering the potential crack was “positive intel,” McGovern said.

Authorities are still trying to determine whether the possible crack has relieved pressure in the tank, a spokesperson for the Orange County Fire Authority told Reuters. Lowering the pressure could help avert an explosion, he said.

Officials focused on measuring pressure of tank

Although officials for now are focused on measuring pressure, the spokesperson said, the crack eventually could allow authorities to gradually drain the chemicals.

On Saturday, Craig Covey, division chief of the Orange County Fire Authority, said the tank’s internal temperature was increasing by about one degree an hour and had reached as high as 90 degrees. But early on Sunday, EPA Administrator Lee Zeldin told CNN’s “State of the Union” program that local officials were working to stabilize the tank by keeping its temperature under 85 degrees Fahrenheit.

“I’m being told this morning that the most likely scenario is one of a low-volume release, where the local authorities are going to be able to monitor, neutralize, and contain the threat,” Zeldin told CNN.

Crews were 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, Covey said.

Health officials have said they ​were concerned that ⁠vapor from the chemical could cause severe respiratory problems with prolonged exposure. Air monitors deployed in Garden Grove were not detecting any chemicals or pollutants on Sunday, the EPA said.

No chemical leak detected

Sensors located around the tank itself have not picked up any chemical leaks in the air, the fire authority spokesperson said.

The Orange County Fire Authority and the Garden Grove mayor’s office did not respond to requests for comment on Sunday. On Saturday, officials 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.

The incident began on Thursday at the GKN Aerospace facility, which specializes in the manufacturing and testing of windows and canopies for commercial and military aircraft, according to its website.

California Governor Gavin Newsom on Saturday declared a state of emergency for Orange County.