The Associated Press

TACOMA, Wash. — An explosion at a foundry was triggered when a propane tanker burst into flames, touching off a series of other blasts, authorities said.

The Saturday blast sent a fireball into the sky over the Atlas Castings and Technology foundry. It could take days to find out why the delivery truck, loaded with 8,000 gallons of propane, exploded, authorities said.

The truck driver, identified as Charles McDonald, 64, was in critical condition at a Seattle hospital Sunday. Three others injured in the blast were released from a Tacoma hospital, authorities said.

An Atlas executive said the company had accounted for all 32 employees who were at the plant Saturday.

A large, two-axle portion of the tanker truck blew more than 150 feet into the air and landed in flames on a highway, state transportation workers told The News Tribune of Tacoma.

The highway was shut down after the blasts but reopened Sunday morning. Engineers had to wait until fire officials determined they could safely inspect bridge piers.

An electrical substation was damaged in the explosions, knocking out power to about 13,000 customers, said utility spokeswoman Chris Gleason. About 200 homes and businesses in the area remained without power Sunday.