The risk of a catastrophic explosion at a damaged chemical tank in Southern California has been eliminated following a close overnight inspection that confirmed a crack in the tank relieved pressure and cooled the chemical, authorities said Monday.

Officials said crews conducted tank temperature checks at night to reduce risks to firefighters, avoiding daytime operations when heat from the tank made conditions around it most dangerous. The overnight mission allowed crews to verify the crack and confirm temperatures were falling, Orange County Fire Authority division chief Craig Covey said Monday morning.

Covey said the results of overnight evaluation of the tank — that the temperature inside had dropped and that pressure had been released — was “incredibly positive news.”

However, evacuation orders remained in place for about 50,000 people in Garden Grove, California, located south of Los Angeles.

Covey said falling temperatures and the release of pressure from the tank were allowing officials to “turn the corner on this incident” after days of concern about a possible explosion.

There has been no chemical leak as of early Monday, but the Orange County Fire Authority said the risk to public safety is “ongoing.”’

Vapors began venting from the site on Thursday

After the tank overheated Thursday and began venting vapors, firefighters have repeatedly sprayed the tank with water in an attempt to cool the chemical inside, methyl methacrylate, which is used to make plastic parts.

The tank’s interior reached 100 degrees (37.7 Celsius) Sunday, an increase of 10 degrees Fahrenheit (5.5 Celsius) since Saturday, according to Democratic state Sen. Tom Umberg. On Monday, Covey said the temperature fell to 93 degrees F (33.9 degrees C).

GKN is a British company that supplies aircraft manufacturers

The tank at GKN Aerospace Transparency Systems, which makes parts for commercial and military aircraft, holds 6,000 to 7,000 gallons (22,700 to 26,500 liters) of methyl methacrylate used to make plastic parts.

GKN Aerospace, a British industrial company, says on its website that it employs about 16,000 people across 32 manufacturing sites in 12 countries and supplies technologies and components used by major commercial and military aircraft manufacturers worldwide.

The Garden Grove facility specializes in aircraft transparency systems, including cockpit windows, canopies and windshields.

Read more here: Associated Press