A firetruck passes the Metro Center metro stop in downtown Washington, April 7. (AP Photo)

The D.C. metropolitan area came to a standstill Tuesday afternoon following what Pepco representatives described as a possible “transformer explosion.” The incident tripped back-up circuits and caused an expansive blackout, interrupting power from The White House and State Department to several stations on the Metrorail system.

Pepco, the D.C. electric services provider, initially said it had scattered reports of outages for “unknown” reasons, and that it was looking into the matter. Government officials later pointed to an explosion at a southern Maryland power facility in Ryceville the likely cause for the regional issue.

Fire and rescue squads throughout Maryland were charged with helping evacuate people trapped in stalled elevators, including those on the University of Maryland’s College Park campus. The university closed shortly after the outage.

More than 100 active outages and 2,179 customers were reportedly affected by the system going into back-up mode around 1 p.m. Pepco said there was “never any full loss of electricity and customers could resume use of street power whenever they wanted.”

Traffic lights across the city and several museums under the Smithsonian Institute complex were impacted by the outage, as well as the National Theater building which loss power in the middle of Oprah Winfrey’s salute to Maya Angelou. Power was restored to most areas in slightly over an hour.