DUNDALK, Md. (AP) — Federal, state and county officials are investigating after a building collapse at the former Sparrows Point steel mill in Baltimore County injured nine workers, four of them critically.

County police and fire departments responded to the former Bethlehem Steel Corp. plant in Dundalk around 10 a.m. Monday. Fire department spokesman Lt. Paul Massarelli says the collapse occurred when the roof of a building being demolished caved in.

Dave Mardigian, a spokesman for MCM Management Corp., which is handling the mill’s demolition, says 13 workers were inside the building and were able to escape on their own.

The workers in critical condition were taken to Shock Trauma, and the others were taken to nearby hospitals.

Massarelli says officials from state and federal agencies and county police will investigate the collapse.

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