ATCHISON, Kan. (AP) — Federal labor officials are recommending a northeast Kansas railcar company be fined $46,900 for violations found after an explosion injured nine employees, two seriously.

The Occupational Safety and Health Administration says it found 11 serious safety violations while investigating a December explosion at the GBW Railcar Services plant near Atchison. Federal investigators say the blast was caused by an electrical heater igniting flammable gas vapors as a railcar was being prepared for cleaning.

Two workers who suffered second-degree burns underwent weeks of skin graft surgery and physical therapy to recover from second-degree burns. The seven others were treated for less-serious injuries.

The company has 15 days to determine if it will challenge the findings.

GBW, based in Lake Oswego, Oregon, manufactures freight cars and barges.