Widespread power outages have been reported across the US capital and its suburbs following an explosion at a power plant in southern Maryland.
The White House, State Department and US Capitol building were all impacted by the outages in the early afternoon on Tuesday.
There was no indication of malicious activity behind the loss of power, the Department of Homeland Security said.
The White House's backup generators kicked on almost immediately, and the mansion was back on regular power a short time later, officials said.
DC Metro Police helped block off access to Pennsylvania Avenue near the presidential mansion as a precaution.
White House spokesman Josh Earnest said there was no indication that the outage was due to a security breach.
"I do not currently see a nexus to terrorism," he said.
Power also went out at the State Department during the daily press briefing, forcing spokeswoman Marie Harf to finish her comments to reporters in an unlit briefing room.
Some Smithsonian museums were evacuated after the power went out.
More than a dozen train stations in the capital also switched to backup power, and officials at the University of Maryland in nearby College Park said the school's entire campus was affected.
The Southern Maryland Electric Cooperative said in a post on Twitter that a "transmission conductor broke free" at its plant in Charles County.
The company said it had restored most service by 2pm local time.
At least 28,000 customers in the metro area were affected, according to officials' counts.
