The National Transportation Safety Board said its investigators would spend between four and seven days examining a train-truck collision in Maryland. Police said a freight train crashed into a truck hauling garbage and derailed in Rosedale, Md., Tuesday, triggering an explosion that shot a plume of black smoke into air and visible for miles, The Baltimore Sun reported. The crash occurred at private grade crossing where the only safety mechanism was a sign notifying motorists to stop, NTSB member Robert Sumwalt said during a news conference Tuesday night. Sumwalt said the NTSB team of rail and hazardous materials investigators would be able to determine the train\'s speed, and a camera mounted on a locomotive should indicate where the truck was when the collision occurred. Authorities said they did not know what caused the crash. The truck driver was identified as John Alban Jr., a retired Baltimore County firefighter who owns a waste collection company near the crash site, the Sun said. A hospital spokesman said he was in serious condition at Maryland Shock Trauma Center Tuesday night. County officials said two rail cars carrying chemicals used to make plastic caught fire. After the crash, authorities temporarily closed U.S. 40 westbound at Rosedale Road, and eastbound at 64th Street. Ramps from Interstates 95, 895 and 695 to U.S. 40 also were closed. The train was traveling from Selkirk, N.Y., to Waycross, Ga. The Sun said the train didn\'t hit any buildings in the industrial area where the collision occurred, but the force of the impact damaged several nearby structures and blew out windows at businesses up to mile away.