WOODS CROSS — Firefighters began a "blitz" approach late Monday in an attempt to suffocate a blaze that erupted at the Silver Eagle Refinery here following a 5:30 p.m. explosion that seriously injured four refinery workers.

Crews began pumping foam into vents on the 42,000-gallon gasoline tank about 9:30 p.m. in an effort to snuff out the fire burning inside by eliminating its oxygen source, said South Davis Metro Deputy Fire Chief Jeff Bassett. If successful, the blaze could be out by about midnight.

Bassett said that would effectively end the need for any evacuation of the surrounding homes as the threat to three nearby smaller tanks would be eliminated.

Police ended the mandatory evacuation order for neighborhoods in a half-mile radius surrounding the refinery about 8:30 p.m. but urged residents to stay away voluntarily.

"It is a voluntary evacuation at this time, but we strongly suggest you stay (at the evacuation center)," Woods Cross Police Sgt. Ekolu Delos Santos told about 100 evacuees gathered at the Woods Cross High gymnasium.

Police assured those at the gym that neighborhoods were being heavily patrolled in their absence.

Flames were seen shooting up into the sky above one of the 42,000-gallon gasoline tanks shortly after the explosion at the refinery at 2355 S.

1100 West, as fire crews from several nearby cities poured water on it. Firefighters early on said they were able to keep the fire from spreading, but were worried about the seams of the tank — and if oxygen should seep in.

"We have the tank surrounded," Bassett said at that time. "We have a large amount of water on it and we're holding it right there. There's no degradation and we don't see tank failure happening."

Four men, ages 30 to 50, at the refinery were injured when the explosion occurred, authorities said, being pulled to safety by co-workers. Two were flown by medical helicopter and the other two were taken by ambulance.

"We have treated four patients on scene," Bassett told the Deseret News. "They have now been transported to the burn unit at University Hospital."

The injuries were described as burns to the faces, necks, arms and hands of the workers. One also suffered lung damage from inhaling the searing heat.

Hospital spokesman Chris Nelson said one man was listed in critical condition, two were serious and one was in fair condition. Their names were not immediately released.