Saint Petersburg: Russia began probing on Saturday the cause of a breakdown at an electricity substation that triggered a massive power cut in Saint Petersburg, its worst urban blackout in half a decade.
The Friday evening cut left almost half of the former imperial capital without power for up to several hours, causing chaos as lights in shops went out, traffic lights failed and metro trains stopped dead in tunnels.
Officials said that seven districts, including the historic centre, were affected, in the worst power cut in a major Russian city since a similarly dramatic blackout hit Moscow in May 2005.
Militants in the troubled Northern Caucasus have repeatedly vowed to strike at Russia`s economic infrastructure but the authorities were quick to rule out the possibility of sabotage.
"I can say for sure that there was no act of terror, or interference from outside," Leonid Belyayev, the head of the Emergencies Ministry for Saint Petersburg, told Russian news agencies.
Officials have said that the blackout was caused by a failure at the Vostochnaya electricity substation outside the city, which then triggered a breakdown at another station further down the line.
"The equipment at the substation is new as it has been in the process of being renovated," the chief engineer of the Federal Electricity Grid (FSK), Dmitry Gvozdyev, told state television.
"We do not think there could have been a breakdown in the main equipment, so we will look for the cause," he added.
The FSK said in a statement on its website that its specialists were investigating the cause of the breakdown. "An initial inspection has not shown any kind of damage to the sub-station`s equipment."
Water supplies were also cut off during the power failure. Mobile phone signals vanished, lifts stopped in the shafts and radio signals could no longer be detected. The deputy mayor said 40 percent of the city was hit.
Electricity was fully restored later Friday and the city was working normally on Saturday.
Russian news agencies said that Vostochnaya sub-station had already been hit by a breakdown in 2006 that caused a major power cut in the city.
Power cuts still occur in some Russian cities due to antiquated equipment but a breakdown on this scale in one of the main urban centres is highly unusual.
Just over one year ago, 75 people were killed in an accident at Russia`s biggest hydro-electric power plant in Siberia blamed on technical failure.