The Moscow public transport system resumed full operation on Thursday following a massive power failure in the Russian capital, state-run Russian television reported.
Industry and Energy Minister Viktor Khristenko told the Russian Cabinet that electricity would be restored in full volume to Moscow by 2 p.m. (1000GMT). Rossiya state television said that some 1,000 residential buildings remained without electricity Thursday morning.
Prime Minister Mikhail Fradkov largely blamed Wednesday's blackout, which affected millions of people in Moscow and surrounding regions, on failures by the Unified Energy Systems monopoly, headed by Anatoly Chubais.
Already on Wednesday, the prosecutor-general's office announced that it had opened a criminal inquiry into the UES management for negligence and abuse of authority. Russian news outlets reported that the electricity utility chief was due to be questioned by prosecutors on Thursday, but UES said he had not yet been summoned.
The outages began with an explosion and fire at a 40-year-old substation, underlining the poor condition of much of Russia's infrastructure. From there it spread in a chain reaction, reaching as far as the Tula region, 200 kilometers (120 miles) to the south.
"We primarily believe that the main reason is that the equipment is worn out," Margarita Nagoga, a UES spokeswoman, said Wednesday.
President Vladimir Putin reacted with a swipe at Chubais, who is despised by many Russians for his role as architect of Russia's much-maligned privatization program of the early 1990s and who went on to be co-founder of a liberal party, where he has frequently criticized Putin.
"I think it's possible to talk about the inadequate attention that the UES leadership has paid to the current activities of the company," Putin said in televised comments Wednesday.
The shutdown of subways and trolley-buses forced tens of thousands of people to reach their destinations on foot or trying to flag down rides. Stores closed down in some regions, while clerks worked by candlelight in others. Managers complained of food spoiling in the heat.
Russian Emergencies Ministry spokeswoman Irina Andrianova said that 20 hospitals lost electricity supplies, forcing them to resort to backup power.
JUDITH INGRAM, Associated Press Writer