PORTAGE | An explosion late Saturday night at Beta Steel Corp. injured four workers, a company official said Sunday.

"We're just grateful everyone is OK," said Joseph Gazarkiewicz, Beta's human resources director.

All four employees were released from area hospitals by Sunday evening after being treated for minor injuries, Gazarkiewicz said. He declined to release their names. Other employees were checked out at the scene and released.

Portage Fire Chief Bill Lundy said the injuries included blunt trauma and burns.

Gazarkiewicz said at about 10:15 p.m. there was a slag eruption in the company's melting shop. Slag is a byproduct of steel production.

A couple of spot fires caused by the blast were extinguished within five minutes of firefighters arriving at the scene, shortly before 11 p.m., Lundy said.

In addition to fire officials, both Portage and Porter County authorities were at the scene, Porter County Sheriff David Lain said. Ambulances from South Haven and Porter hospital also responded.

Gazarkiewicz said the cause of the explosion currently is undetermined and is under investigation. A spokesman for the Indiana Occupational Safety and Health Administration had no information about the accident Sunday afternoon.

Beta Steel produces hot-rolled coil for steel service centers and tube and pipe manufacturers.

It also has an electric arc furnace with a 700,000-ton annual production capacity and a 60-inch hot-strip rolling mill with a 1.1 million-ton annual production capacity.

Times Staff Writers Robert Blaszkiewicz, Deborah Laverty and Kathleen Quilligan contributed to this report.