A transport vehicle that can carry up to 400 tons of molten steel was backing into a building when some of its high-temperature cargo sloshed out, said William Hornberger, a spokesman for Severstal North America, Inc.

The molten steel hit two of the vehicle's eight-foot tires, setting them afire and causing them to explode minutes later as Dearborn firefighters battled the fire, Hornberger said.

"We were very fortunate that none of the people were standing in harm's way when the tires blew," he said.

Hornberger said four of the injured people were Severstal employees — three supervisors and a company firefighter.

Two Ford Motor Co. firefighters and a city of Dearborn firefighter were also hospitalized.

Three other firefighters were taken to Detroit Receiving Hospital.

The Rouge once was the world's largest industrial complex. The steel plant previously was owned by Ford Motor Co. and currently is owned by Severstal, a Russian steel company. The companies share the complex.

The Rouge plant has been the site of several accidents in the past few years. In 1999, a Ford boiler undergoing routine maintenance exploded, killing six employees and injuring 14 others. State regulators later found 15 workplace safety violations.