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© RT Photo/Gayane Chichakyan
Lights went out at the State Department, White House, Capitol and many other places in Washington, DC, in a puzzling series of power outages. Terrorism is not suspected, officials say.

Power went out at the State Department during the question-and-answer session on Iran nuclear talks.
Power goes out at @statedept during @mariehark briefing during q and a on #Iran nuclear deal transparency issues...

— Matt Lee (@APDiploWriter) April 7, 2015
After the initial confusion, the briefing continued.
The State Department press briefing continues in darkness. Power outage pic.twitter.com/Ph9Zytt7Hp

— Gayane Chichakyan (@Gayane_RT) April 7, 2015
Acting State Department spokeswoman, Marie Harf, continued the session under what appeared to be light from a smartphone.
Pepco's current outage map for downtown DC pic.twitter.com/8o4PRyUayo

— erin mccann (@mccanner) April 7, 2015
Outage at State seemed to be part of a widespread chain of power failures around Washington, DC, for "unknown" reasons. Reports are coming in from a number of government buildings, metro stations and offices downtown, including the White House and the Department of Justice.
The subway serving the Dirksen and Hart #Senate office buildings is temporarily out of service. The walkway remains open.

— SenateSergeantAtArms (@SenateSAA) April 7, 2015
Washington Metropolitan Area Transit Authority (WMATA) reported 13 stations on emergency power.
Metrorail counts 13 stations on backup power. Locations widespread, including Anacostia, Dupont, Minn Ave, Pr George's Plaza, Navy Yd.

— Dr. Gridlock (@drgridlock) April 7, 2015
Several office buildings downtown have been evacuated.
@nbcwashington people being evacuated out of their buildings downtown due to a power outage 20th st nw and e st nw pic.twitter.com/HrOlrzvLkb

— NBC PHOTOG (@bforte22) April 7, 2015
The University of Maryland, in the suburb of College Park, also lost power.
There is a campus-wide power outage. Crews are working on addressing the problem. Thank you for your patience.

— Wallace D. Loh (@presidentloh) April 7, 2015
Smithsonian Institution museums downtown were also affected. Four museums were evacuated, including the popular National Air and Space Museum.
If/when power is restored, we will reopen the buildings. We do not know when that will be at this time

— Smithsonian (@smithsonian) April 7, 2015
Potomac Electric Power Company (PEPCO) has not officially confirmed the cause of the outage, but said that by 1:15 PM local time there were 111 active outages and 2,467 affected customers.

According to Washington Post reporter Aaron C. Davis, Homeland Security officials believe the cause of the outage was due to an "explosion" at the Southern Maryland Electric Cooperative (SMECO) power facility in southern Maryland.

US government officials told Reuters there were "no initial indications" terrorism was involved.