For several years, emergency intercoms weren’t working in scores of Metro cars, the transit agency said Wednesday.

The problem, which affected cars that were arranged in certain configurations, meant that riders had no way to reach train operators. Beginning Tuesday night, Metro rearranged dozens of trains, providing a temporary fix to the problem. Intercoms were working when the system opened Wednesday, the agency said.

Metro spokesman Dan Stessel said that although Metro had received customer reports of failing intercoms “for some time,” only this week was the agency able to identify the cause and devise a solution. Stessel would not say what led engineers to pinpoint the issue after so long, nor would he say how long engineers had been looking into the issue.

After a fight aboard a Red Line train on Monday, rider reports from the scene indicated that passengers were unsure if they were able to reach the train operator over the intercom. Stessel said he did not know whether Metro’s actions this week were in response to the reports Monday about the Red Line.

The transit agency was aware of a general problem with the intercoms at least four years ago. After the Red Line crash that killed nine people that year, Metro began placing older cars from the 1000 series in the middle of train sets, between newer cars from the 6000 series.

But Metro acknowledged in a news release that year that arranging cars that way could cause the intercoms to fail. It said officials were “seeking to identify a fix to that situation.”

“I would assume we’re talking about the same issue,” Stessel said Wednesday. “This issue has existed for as long as [the] 6000 series car has been on the property.”

The newer cars were introduced in 2006.

Stessel said he did not know why trains in the 1000 series were still trailing cars in the 6000 series nearly four years after the issue was raised. The Washington Metropolitan Area Transit Authority has launched a review that will cover whether the problem could have been detected earlier, and the results of the review will be presented at a meeting of the board’s safety committee.

In the meantime, Metro had to rearrange about three dozen of the 140 trains it operates daily before opening the system Wednesday. Safety workers will perform random intercom inspections.

The Tri-State Oversight Committee, which monitors Metro’s safety practices, formally requested in April that Metro investigate the issue.

“It’s a passenger feature that needs to work and needs to work reliably,” said Jim Benton, who heads the committee.

After an NBC 4 investigation into intercom problems this year, Mort Downey, chairman of the Metro’s Safety and Security Committee, said that board members were told the intercoms were working.

“The question I would ask is, how come we heard there wasn’t a problem, and now it turns out there was a problem?” Downey said.

Intercoms failed on trains where cars from the 6000 series, the newest in Metro’s fleet, were followed by older cars from the 1000 or 4000 series.

Making long-term fixes requires hardware and software changes. Metro said it will be able to make the changes to fix the problem on the 1000 series cars in 45 days, but it’s unclear how long it will take to make changes for 4000 series cars.