Power outages in Moscow strand thousands in Metro

Power outages in several regions of Moscow have stopped public transit in its tracks and stranded people trying to get around the city in the middle of a minor heat wave. Echo of Moscow and Lenta.ru websites are currently inaccessible (to me, anyway), probably overloaded with people checking on the situation, RIA Novosti reports that 15 hospitals were left without power and that people are being evacuated from those portions of the metro that were left without power. RIA Novosti's most recent English-language report (I couldn't access the text of this page for a few minutes, either) is headlined "Close to 20,000 people stuck in metro tunnel over power outage":

MOSCOW, May 25, 13.07 (RIA Novosti) - "Forty-three trains are stuck in the metro line section from Serpukhovskaya station to Bulvar Dmitriya Donskogo. There are a total of 20,000 passengers in the tunnel," the Moscow Metro's press service told reporters.

On the RBC wire I see that RAO UES does not exclude the possibility of terrorist involvement, although that seems far-fetched at this point.