MBTA GENERAL MANAGER Steve Poftak said on Monday that a tool cart being used to lay 1,8900 feet of new track on the Blue Line derailed three times, not the one time cited by T officials last week in announcing a second delay in reopening the subway service.

Poftak said the derailments were properly reported to the Federal Transit Administration, but T officials did not disclose them to the public. Indeed, T officials last week were not forthcoming about the Blue Line situation when asked directly about derailments.

“Derailments are never a good thing, but just to clarify these were not Blue Line vehicles, they were not revenue vehicles. These were tool carts being used for construction,” Poftak told reporters on Monday.

Asked why the derailments were not disclosed earlier, Poftak said: “I’m sharing that with you now. I don’t know the strategy of not doing it previously, but I wasn’t involved with that.”

A portion of the Blue Line was shut down for two weeks to lay down 1,800 feet of new track and make other repairs inside the subway tunnels. On Sunday May 8, the day the Blue Line was scheduled to reopen, the T announced the closure was being extended until Friday “to finish scheduled work and complete additional work.”

Sources had told CommonWealth on May 9 that the extended closure of the Blue Line was due at least in part to the derailment of a test train running over the newly laid track.

T officials insisted no test trains had derailed. Asked if some other type of repair vehicle had derailed, the T officials did not respond.

Five days later, the T announced the Blue Line closure would be extended until Wednesday because of the derailment of a tool cart.

“There were no injuries,” the T said in a statement. “The process to re-rail the tool cart earlier this week and make other repairs while continuing to finish scheduled work means additional time is needed to safely complete the project.”

T officials at that time again refused to comment on other derailments, and now Poftak is saying there were three in all. He said he did not know when each derailment occurred.

Poftak said the Blue Line is scheduled to reopen on Wednesday after every inch of the new track is carefully inspected.

The lack of disclosure about what happened on the Blue Line is similar to what happened when the  Federal Transit Administration assumed “a safety oversight role” at the T following a series of safety incidents at the transit authority. Although the FTA notified the T of the new oversight role by letter on April 14, neither the T nor the FTA confirmed the existence of the FTA’s new involvement until several weeks later after the letter was leaked to the Boston Globe.

At a safety subcommittee meeting of the MBTA on Monday, the T’s chief safety officer said the FTA probe began last week and will continue for at least several weeks. The T official said findings might be released by late summer.