MOSCOW, June 20 (RIA Novosti) - The two transformers at the Chagino substation that caused the blackout in this city and its surrounding regions in May date back to 1958 and 1960, said Anatoly Chubais, the head of Russia's energy giant Unified Energy Systems (UES).

"The Chagino power substation has 122 similar transformers which have been in operation for more than 40 years," said Chubais. "It reflects the grave problems our company and the entire power sector, if not the entire infrastructure of the country, are facing."

Chubais reemphasized that he and his company were responsible for the blackout.

"I think we - and I personally - bear the responsibility," he said.

Chubais said that power losses in Moscow at around noon on May 25 had been registered at about 2,500 MW. He said this figure equaled a quarter of power consumption in Moscow at that time of the day.

"The accident affected at least four million people. About 20,000 were stuck in the metro, and another 1,500 in elevators," Chubais said. "We think the accident was very serious."

He described the reasons for the accident as "classic," saying a company probe had established mistakes committed by operating personnel and a failure in the distribution network.

Chubais also said dramatic power cuts happened in Moscow in 1949.