ST. LOUIS (AP) -- Following an explosion at a St. Louis area manufacturing plant, officials say at least two people are in critical condition.

Authorities say 10 people were taken to hospitals after the explosion Thursday at the American Steel Foundries plant in Granite City, northeast of St. Louis.

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Granite City Fire Capt. Bert Houston says the explosion occurred after gas caught fire in the finishing area of the plant, which makes railcar components. What ignited the gas wasn't known.

Gateway Regional Medical Center spokeswoman Kate Allaria says seven workers treated for smoke inhalation have been released. She says three other injured workers were flown to other hospitals.

A spokeswoman at Mercy Hospital in Creve Coeur says the two victims it received are in critical condition. The whereabouts of the other worker was unclear.

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