The largest disaster drill since September 11, 2001 at the World Trade Center site took place this morning. New York City officials staged a mock explosion on a PATH commuter rail train in the tunnel linking Lower Manhattan, at the World Trade Center terminus, to northern New Jersey. Hundreds of police officers, firefighters and Port Authority of New York and New Jersey officials participated, along with 150 volunteers who pretended to be victims of the explosion. City officials advised downtown residents in advance of this drill. PATH rail service was suspended Sunday morning until the drill was completed.