The MBTA has announced it will delay putting a new fleet of Orange Line cars into service — again.

The cars were initially supposed to be rolled out in January, and in January the date was pushed back to "early spring."

But during a meeting Monday, Deputy General Manager Jeff Gonneville said testing on the cars won't begin until late April and May.

"What that means is that we will not be able to introduce our first set of cars until this summer," Gonneville said.

He said the delays are due to a software issue that was identified during early rounds of independent testing required for the cars' signal system. The software had to be modified and is now being tested in a lab before the MBTA can begin its own tests.

So far, though, 10 new Orange Line cars have been delivered to Boston, the MBTA said. It expects all 152 to make their way here by December 2021.