A MARC train experiencing mechanical problems on the Penn Line north of Washington, D.C. has caused all northbound service to cease for nearly an hour. 

Train 428, scheduled to leave Union Station at 4:15 p.m., broke down north of Union Station. The train began moving shortly after 5 p.m., but at a reduced speed. Several northbound trains following train 428 were running with delays of between 40 and 60 minutes.

Metro will honor MARC passes.

This is a developing story and will be updated as events warrant.