Illegal migrant workers who were kicked out of the Trade Union Center in Paris after occupying its offices for the past year, camp outside its entrance, July 6, 2009, in a last push to obtain the straightening out of their status. Illegal immigrants working in the Paris area have launched an unprecedented wave of sit-ins and strikes to demand their situation be normalized, challenging France's tough stance on immigration.
Investigators are working the scene to determine a cause. One train apparently rammed a stationary train on the system's Red Line. One of the dead was identified as the operator of the moving train.
The Washington Post cited signal system failure and operator error as possible causes of the accident.
The force of the impact crushed the rear car of the sitting train "like an accordion," witnesses said, and forced the moving train into the air. It landed atop the other train.
Rescue crews searched the wreckage and surrounding area for victims. The Post said five bodies were removed from the crash debris Tuesday morning.
Commuters Tuesday were warned to avoid using the Red Line if possible. The Red Line is the busiest section of Washington's Metro system.