ATLANTA >> A sudden power outage brought the world’s busiest airport to a standstill today, grounding scores of flights in Atlanta just days before the start of the Christmas travel rush. However, authorities said that electricity should be restored at the Hartfield-Jackson AtlantaInternational Airport by midnight.

Passengers at the airport were left in the dark when the lights suddenly went out at around 1 p.m. The blackout halted all outgoing flights, and arriving planes were held on the ground at their point of departure. International flights were being diverted, officials said.

According to a Georgia Power statement, a fire in an underground electrical facility may have been responsible for the outage. The cause of the fire was not known.

“No personnel or passengers were in danger at any time,” the statement said.

No areas outside of the airport were affected by the power loss. The utility said that there are “many redundant systems in place” to ensure the power supply to the airport and that such outages at the airport “are very rare.”

Officer Lisa Bender of the Atlanta Police Department said officers were at the airport to help with crowd control and managing traffic around the airport.

Delta Air Lines, which has its headquarters at the airport, said more than 450 mainline and regional flights were cancelled. The airline encouraged passengers to check on the status of flights via the Fly Delta mobile app or delta.com before heading to the airport.

At Southwest Airlines, about 70 Atlanta departures out of 120 scheduled for today were cancelled, an airline spokesman said in an email.

Delta passenger Emilia Duca, 32, was on her way to Wisconsin from Bogota, Colombia, when she got stuck in Atlanta. She said police made passengers who were in the baggage-claim area move to a higher floor. She said restaurants and shops were closed.

“A lot of people are arriving, and no one is going out. No one is saying anything official. We are stuck here,” she said. “It’s a nightmare.”

Mozell Smith, 68, of Atlanta arrived at the airport hours after the electricity went off. He was headed to Las Vegas with a sister and a friend.

“This is terrible. I wish someone would’ve given us a heads-up before we got to the airport,” he said. “I wish there would have been better communication.”

American Airlines reported only a handful of diversions and cancellations because the carrier does not use Atlanta as a hub, airline spokeswoman Alexis Aran Coello.

Hartsfield-Jackson, which serves 104 million passengers a year, is the world’s busiest airport, a distinction it has held since 1998.

The airport serves an average of 275,000 passengers daily, according to its website. Nearly 2,500 planes arrive and depart each day.