The District's 911 system went down for 90 minutes over weekend because a building engineer hit an all-stop emergency shutoff button, officials said Monday.

The city's 911 system stopped working Saturday night after 11 p.m. It was back in service by about 1 a.m., said officials, including Mayor Muriel Bowser, who tweeted updates during the outage.

The engineer who hit the button at D.C.'s 911 call center was looking for a plumbing leak that threatened highly sensitive equipment.

D.C. emergency officials plan to add more security and signage to limit access to the button involved in the outage.

Chris Geldart, director of the District of Columbia's Homeland Security and Emergency Management Agency, said Sunday that power from Pepco flowed normally into the system and was not the source of the failure.

Geldart said Sunday it was not a normal type of failure, but there was nothing nefarious about it, and there was no hacking into the system.

Officials did not have an accurate number of missed calls during the outage.

The fire and EMS department said they received 30 EMS calls and five fire calls to the 10-digit backup number used during the outage. The police department said they had five dispatch calls.