The multibillion-dollar Second Avenue subway line is operating without a working fire alarm system.

Fire alarms in the three-stop expansion have been shut off since May 14 for a complete reprogramming, according to an internal memo sent from the MTA to its board, which was first reported by Politico and confirmed by amNewYork.

On that Sunday, May 14, a “false activation” of the alarms in the 86th Street station led to a weeklong shutdown of its 83rd Street entrance. The activation damaged the entrance’s escalators and required contractors to reprogram the entire fire alarm system. That process won’t be completed until December.

Without a working alarm system, the MTA is spending $6.5 million to pay fire safety professionals to be stationed along the line, serving as an around-the-clock fire watch. MTA spokesman Shams Tarek said costs would be recovered from contractors.

“The MTA will not pay for this cost and will file claims against the responsible parties involved to recoup any and all money that we are spending as a result of the false activation of the fire system — that includes the cost of the fire watch,” an MTA representative said. “Meanwhile, Second Avenue Subway is open, safe, serving roughly 170,000 riders a day and reducing pressure on the Lexington Avenue Line.”

Facing potential delays, Gov. Andrew M. Cuomo made it his personal responsibility to open the Second Avenue subway by the start of 2017. Transit experts have lauded the $4.5 billion project for reducing crowding in the nearby Lexington Avenue line and on streets above, but reports have questioned the stations’ readiness for service.

Last month, The New York Times said that as the line was opened, there were 17,000 “defects” and the MTA was still conducting safety checks.