By CBSBoston.com Staff

BOSTON (CBS) — The MBTA said Monday that it can’t say when new Orange and Red Line cars will be able to return to service, though it may know more next month.

During a meeting, a T official said an investigation into March’s Orange Line derailment shows all of the new cars were “acting abnormally” and the problem got worse as mileage on the cars started to add up.

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The problem has been traced to pads that are gripping harder as they wear down. The T built a new testing area at Wellington Circle to try to figure out why this is happening.

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The T plans to give an update at a meeting on June 7 and hopefully have a plan by then on how to safely bring the trains back into service.

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The MBTA has made a $2 billion investment in the Orange and Red Lines. The agency has said there will be 152 new Orange Line cars in service by 2022.

CBSBoston.com Staff