Metro is now inspecting all of its 5000 series rail cars after determining that those cars may have been involved in an incident Tuesday during which the doors on another car opened while a train was moving.

The transit agency has been investigating what caused the doors to open on two 1000 series rail cars on the Red Line while the train was in motion during the Tuesday morning commute.

Crews were able to successfully replicate the incident in a rail yard on Thursday, Metro spokesman Dan Stessel said.

They now believe that a piece of equipment was misaligned, perhaps because of a problem on the two 5000 series cars just ahead of the 1000 series cars on which the doors opened. The equipment may have been damaged when the cars were coupled together.

But Stessel said the “failsafe features of the train worked as designed, automatically applying the brakes to bring the train to a stop when the events occurred.”

Metro was planning to start inspecting all 190 cars of the 5000 series for similar issues on Friday afternoon. Stessel said it would likely take about two weeks. The cars will still be used during that time, unlike in July 2010 when the agency pulled all 4000 series cars from service when it feared doors could open while trains were running.

"We do not believe it's anything systemic to the fleet so we're not pulling the cars," Stessel said.