[This post has been updated]

Metro’s Red Line riders experienced delays Wednesday night around 9 p.m. after a computer problem at the transit authority.

Dan Stessel, Metro’s chief spokesman, said there was “a computer issue” with a system that tracks the “manual control of trains through work zones.”

Controllers use the system, he said, to move trains from one track to another when work is being done. Wednesday night trains were single-tracking between Van Ness and Medical Center.

Stessel said that when the system to move trains from one track to another is down “you can no longer single-track because you can’t switch the train from one another.”

That meant the track also had to be cleared of workers for safety.

The trouble meant riders were stuck on trains at Medical Center and Cleveland Park. Metro said the passengers were delayed on trains 20 to 30 minutes. But some riders complained on Twitter that their waits were slightly longer.

Stessel said that officials are trying to determine the cause of the problem.

Metro is undergoing an aggressive capital program to try to rehab its stations, escalators and track work. The $6 billion program includes regular work on the Red Line that repeatedly causes delays and frustrations for riders.

Update, 5 p.m.: There were tweets from Metro saying that there were no problems with train movements on the Red Line. On Thursday, Dan Stessel, Metro’s chief spokesman, said those tweets were sent because they were “based on the best information available at the time.”

He wrote in an e-mail Thursday that it’s “easy to second guess this stuff 19 hours after the fact.” He said he was in touch with Metro’s rail operations center and “they confirmed that trains were moving on all lines, and with the exception of two trains, that was accurate.”

He further wrote that the “computer issue did not affect train movement outside of work zones.”  

“The point we were making was that the issue was not similar to the Jan. 26 incident, as some were speculating,” he said, referring to a power outage that caused delays on the Blue, Red and Orange lines.

Follow me on Twitter @postmetrogirl.