Atlanta Mayor Kasim Reed said Sunday night that a fire led to a power outage earlier in the day that stranded thousands of passengers at Hartsfield-Jackson Atlanta International Airport, but the cause of the fire is still unknown.



The fire in an underground tunnel knocked out the main power source and the airport’s backup system, Reed said in a press conference. The strength of the fire forced Georgia Power, the city’s utility company, to wait before it could begin fixing the issue, he said.

Georgia Power said earlier Sunday it expected to restore electricity to the airport by midnight, which Reed reiterated.

There is no evidence that the fire was caused deliberately, but the cause is still under investigation, the mayor said.

Reed apologized to passengers who spent the day stuck on airplanes outside the airport and in the terminals.

The power outage affected tower reception outside the airport. As a result, all flights were canceled, and a stop was put in place on incoming flights.

The city is opening its convention center, which can accommodate up to 10,000 people, to those affected by flight cancellations, Reed said.