Power company Pepco did not say what caused the outage, only that they were investigating the problem.
“We are currently looking into the cause and will provide more details as soon as we receive an update,” Pepco posted on Twitter.
The State Department in the US capital went dark in the middle of a press briefing, an AFP reporter said, and the press conference continued briefly in the dark.
State Department officials told reporters the power company said electricity could return in the coming hours.
Several metro stations were on emergency lighting, but trains continued to run.
Metro police said on Twitter “units responding to assist at all stations affected by power outages. No elevator entrapments reported at any station.” – AFP