Tacoma Deputy Fire Marshal Kevin O'Donnal said two large propane tanks exploded during a refilling operation at the foundry at 3021 South Wilkenson around 3 p.m. The fireball went an estimated 500 feet into the air.
A man in his 60s was severely burned and was airlifted to Harborview Medical Center in Seattle where he was listed in critical condition.
Three workers were taken to St. Joseph Hospital. Two suffered leg injuries and a third suffered facial burns. All three were released late Saturday.
The explosion left a two-alarm fire for firefighters to control, and crews also prevented a third propane tank from exploding.
O'Donnal said a power substation also exploded, which may have been the cause or the result of the fire. He said it may take investigators several days to determine exactly what happened due to the extensive damage to the industrial building.
Joe Farmer, supervisor of the cleaning room at Atlas, was nearby when the first explosion occurred.
"It blew me off the forklift," Farmer said. "It blew out several windows. All of the buildings nearby used to have junk all over the tops of them. It's not there anymore."
Farmer estimated that between 30 and 40 people were in the foundry on Saturday.
"I'm not usually one to get too frightened. But I was pretty frightened," he said.
A woman who lives two blocks from the Atlas foundry said she heard and saw three big explosions at the Tacoma industrial plant. Carvedia Martin said the first blast was like an earthquake so she ran outside and saw the plume with flames shooting through it. The heat was so intense she covered her face.
"The cloud was so intense, you know, it looked like the bomb at Hiroshima," Martin said. "As I stood, the flames just rolled straight up in the air - the gas and the fire. That's when I turned and ran."
Martin said there was a second blast about 12 minutes later after firefighters arrived, and then a third explosion. She said the heat was so intense she had to cover her face.
Alan Bouman, a worker at T&T Tire Factory a couple of miles away, said the blast caused lights to flicker and a door to sway open.
"Some of the guys outside asked if you heard that, heard the explosion," Bouman said.
Matthew Washam, who is in the area, said police have continued to move onlookers farther away from the scene. He said there were multiple explosions and flames continued to shoot from a venting propane tank on the site.
The foundry, which traces its history back to 1899 when the company made iron castings for the Northwest logging industry, is near the intersection of I-5 and Highway 16.
The incident triggered several road closures in the area. The eastbound lanes of State Route 16 is stopped at Union Avenue. The southbound lanes of Interstate 5 were closed for a time just north of the exit to the westbound lanes of State Route 16. The northbound lanes were also closed at 38th Street, but the interstate has since reopened in both directions.
The explosion initially left 13,000 customers without power, but power was restored to all but 200 customers. Officials said damaged power lines may need to be fixed before power can been restored to the remaining customers, but said work cannot begin until fire officials rule the area is safe.
Destruction, debris and flames are clearly visible in this aerial photo of the Atlas Castings & Technology plant. (Joshua Trujillo / P-I)