Power Outage Hits White House, Lights Go Out in Washington Area

A power outage hit the White House and much of the Washington area on Tuesday, snarling trains, emptying museums and cutting electricity to government buildings and the U.S. Capitol for hours.

The Justice Department and State Department were among thousands of customers affected, along with the University of Maryland and some World Bank offices.

Power company Pepco Holdings Inc said the outage stemmed from a dip in voltage because of transmission line trouble. The Department of Homeland Security said there was no indication the outages had been caused by malicious activity.

The outage was centred in downtown Washington, where much of the government offices are located, before power was largely restored a few hours later.

White House offices and the press room went dark briefly before backup sources kicked in. President Barack Obama was in the Oval Office and did not notice the power failure, spokesman Josh Earnest told a news briefing.

"Things are slowly but surely returning to normal here in the White House complex," he said.

The State Department's daily briefing was suspended after power was lost. At the U.S. Capitol complex, a backup generator switched on, keeping most lights and appliances running.

At least four Smithsonian museums were evacuated, including the Natural History Museum on the National Mall, where the power failure left hundreds of visitors milling around outside.

"It was just dark and a lot of people there and it was dark and it was awkward. Because, like you couldn't see anything, you're just standing there and the lights are off," tourist Karina Coulter told Reuters Television.

Power also went out as media tycoon Oprah Winfrey was speaking at a Postal Service ceremony marking the issuance of a stamp honouring poet Maya Angelou.

Some subway stations in the United States' second-busiest transit system ran on backup power.

Pepco said its crews were repairing transmission equipment in Charles County, Maryland, south of Washington. The company's website showed about 1,600 customers without power.

Robyn Johnson, a spokeswoman for the District of Columbia homeland security office, said there was speculation that an explosion about 12:30 p.m. EDT at a plant south of Washington operated by the Southern Maryland Electric Cooperative had caused a power surge that cut electricity.

The power company did not immediately respond to requests for comment.

Admiral Bill Gortney, commander of North American Aerospace Defense Command and U.S. Northern Command, said at a Pentagon news briefing he had been told all backup systems had kicked in.

But he will be checking to see "did they perform as advertised?" he said.