TOKYO (AP) _ Two passengers were killed and at least 16 others injured when a rush-hour subway train derailed and was grazed by a train coming in the opposite direction Wednesday morning, officials said.

Tokyo Fire Department spokesman Fukuo Isozaki said that along with the two dead passengers, another three remained unconscious shortly after the accident.

He said 16 others were injured.

The cause of the accident was not immediately known, said spokesman Ryuichi Kinoshita of the Tokyo Rapid Transit Authority.

Television news showed a side of a car of the train was torn off, possibly when the derailed train hit the train coming in the opposite direction on a parallel track.

There were reports of that more passengers were likely injured in the accident, but officials could not immediately confirm that.

Kyodo News agency reported that the train had been derailed by an explosion inside one of the cars, but Kinoshita said he had no information about the report.

The train derailed at 9:03 a.m. Wednesday at Nakameguro Station, the western terminus of the heavily traveled Hibiya Line, he said.

Service has been resumed on part of the line, he added.