A U.S. Secret Service Uniform Division patrol vehicle blocks eastbound traffic at the intersection of 18th Street NW and Pennsylvania Avenue after an electrical blackout affected the White House and other government buildings in the area on April 7, 2015 in Washington, D.C. (credit: Chip Somodevilla/Getty Images) A U.S. Secret Service Uniform Division patrol vehicle blocks eastbound traffic at the intersection of 18th Street NW and Pennsylvania Avenue after an electrical blackout affected the White House and other government buildings in the area on April 7, 2015 in Washington, D.C. (credit: Chip Somodevilla/Getty Images)

UPDATED: April 8, 2015 9:15 a.m.

WASHINGTON (CBSDC/AP) — Problems at a Maryland electrical station caused widespread power outages across the nation’s capital Tuesday, affecting the White House, the Capitol, museums, train stations and other sites.

Many of the outages were brief, but some were longer and forced evacuations. Officials said a mechanical failure at a transfer station led to the outages, and terrorism was not suspected. Tens of thousands of customers lost power.

At the White House, the interruption last only a few seconds before backup generators kicked on. The complex quickly went back onto regular power. Electricity in the press briefing room dipped around lunchtime, briefly darkening cubicles and blackening TV screens.

White House spokesman Josh Earnest said he was with President Barack Obama in the Oval Office when the power blip occurred, and they didn’t notice anything unusual.

Power also went out at the State Department during the daily press briefing, forcing spokeswoman Marie Harf to finish her comments in the dark.

Power in the U.S. Capitol building twice shut down briefly, and then came back on by way of a generator.

The root of the problem was actually an electrical station located about 35 miles southeast of D.C. in Charles County, Maryland.

A mechanical failure occurred shortly before 1 p.m. Tuesday at a transfer station there, which is controlled by utilities serving both Washington and southern Maryland.

Homeland security officials in Washington and Maryland confirmed there was an explosion at the station.

In a statement released later Tuesday afternoon, the Southern Maryland Electric Cooperative (SMECO) said a Pepco transmission conductor broke free from its support structure and fell to the ground.

Pepco says there was never a loss of permanent electric supply but rather a dip in voltage that caused equipment at some facilities to transfer to backup systems. The momentary outage occurred because of equipment in individual buildings throughout the area responding to the dip.

Some effects of the incident were still apparent later Tuesday afternoon. Some traffic lights were out, and Metro said several public transit stations were affected. Power to the trains remained on and trains were moving, Metro spokesman Dan Stessel said, but the affected stations were on emergency power, with dimmer lighting and nonworking elevators and escalators.

The Bethesda Metro station remained closed for six hours because of an escalator outage caused by the surge.

Some Smithsonian museums also lost power, were evacuated and closed to the public, including the popular National Air and Space Museum and the National Portrait Gallery, a spokeswoman said.

Thousands of tourists spilled from the museums onto the National Mall. It’s a busy time of year for tourism as spring brings both better weather and the National Cherry Blossom Festival, which draws thousands to look at the pink-budded trees.

In a statement released later Tuesday afternoon, SMECO said the explosion was caused by a transmission conductor that broke free from its support structure and fell to the ground.

By officials’ counts, at least 28,000 customers in the metro area were affected.

PHOTOS: Major Power Outage in D.C. & Md.

The University of Maryland campus in College Park closed at 2 p.m. due to the outage.

Prince George’s County Fire Department officials said the department conducted several elevator rescues on campus.

Power was restored to the entire campus around 4:50 p.m.

WNEW’s Chuck Carroll contributed to this report. Follow him and WNEW on Twitter.

WNEW’s Cameron Thompson contributed to this report. Follow him and WNEW on Twitter.

(TM and © Copyright 2015 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2015 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)