A string of four Amtrak locomotives slammed into the side of a Conrail coal train Friday, injuring two Amtrak trainmen.

An investigation determined that the brakes were improperly engaged in three towed locomotives being pulled by the lead engine, said Jim Burnett of the National Transportation Safety Board.One of two blocked tracks on the heavily traveled Northeast corridor reopened about 12 hours after the 3 a.m. crash, and Amtrak said the second track would not be in service until Saturday. Roughly 20,000 people travel the line daily.