Parts of D.C.’s suburbs and the District — including the White House, the State Department and museums along the National Mall — experienced power outages Tuesday after problems at an electrical facility in Southern Maryland.
Some of the outages were brief, especially in places like the White House, where emergency generators kicked in almost immediately. But others were prolonged, causing frustration and confusion among the region’s nearly 20,000 affected electric customers.
Officials quickly said that terrorism was not suspected as a cause for the widespread outages.
Nicole Chapple, a spokeswoman for the District’s Department of Homeland Security and Emergency Management, initially said an explosion at an electrical facility operated by Southern Maryland Power Cooperative (SMECO) caused the outage.
SMECO later released a statement saying that a transmission conductor fell from a support structure at a cooperative facility in Charles County at about 1 p.m. The mechanical failure caused outages at two SMECO facilities and interrupted the flow of electricity to two Pepco facilities.
The cooperative rerouted power through Calvert and St. Mary’s counties to restore service to SMECO’s 17,000 customers affected by the outages by 2 p.m.
At the height of the outages, Pepco reported nearly 2,500 customers were without power.
“There was never a loss of permanent electric supply but a dip in voltage caused equipment at some facilities to transfer to backup systems,” Pepco said in a statement.
Meanwhile, Metro reported that 13 train stations were on backup generators as a result of the outage.
Parts of the White House complex had to rely on backup generators for a short time, administration officials said.
Sections of the complex, such as the press briefing room, lost electricity for just a few seconds. Other parts of the White House were completely unaffected, and President Obama himself was unaware of the outage until after full power had been restored, White House press secretary Josh Earnest said.
“I was with the president, and he did not notice,” Mr. Earnest told reporters. “The impact on those of us working at the White House was minimal.”
Mr. Earnest said there are no indications the power outage was related to terrorism, though he did say the Department of Homeland Security continues to look into the situation.
At the State Department, spokeswoman Marie Harf was forced to complete her daily press briefing with the light on an iPhone when the lights went out there.
Power in the U.S. Capitol twice shut down briefly, and then came back on by way of a generator.
Adm. William Gortney — commander of U.S. Northern Command, which is tasked with homeland defense — was visiting the Pentagon when the outage hit.
In the days ahead, Adm. Gortney said he will look at if backup systems worked properly and were adequate to keep key buildings secure during the outages, or if more systems need to be put in place. Just hours after the outage, he said initial indications showed that everything worked as it was supposed to.
“At the moment what I’ve been told is they kicked in and they are working, everyone is back up on backup power,” he said. “So as we look forward to look at how well those back up systems did work, did they perform as advertised? Do we need to strengthen them in some areas?”
⦁ Ben Wolfgang and Jacqueline Klimas contributed to this article.