NEW YORK, June 27 (Xinhua) -- A power outage hit the Upper East Side of Manhattan and parts of the Bronx on Wednesday afternoon, cutting the subway service and forcing the evacuation of the Metropolitan Museum of Art.

    Mayor Michael Bloomberg, who lost power Wednesday at both his private home and Gracie Mansion, the official mayoral residence, shrugged off the blackout as "a minor inconvenience to people."

    New York City Transit spokeswoman Deirdre Parker said the power failed at 3:40 p.m. (1940 GMT) and was out until about 4:45 p.m. (2045 GMT).

    The 4, 5, 6, E and Z subway lines were affected in Manhattan and the D line was affected in the Bronx. A portion of the A and Clines were also out, from Harlem to the Bronx.

    The power outage caused suspensions and delays along the city's subways, but the blackout mainly affected track signals and not the movement of trains or air conditioning in the cars.

    Officials at the Metropolitan Museum of Art said the museum lost power around 3:45 p.m. and had to be evacuated, but power has since been restored.

    The energy company Con Edison said that about 385,000 people throughout the West Bronx and the Upper East Side were left without power around 3:40 p.m.

    In the West Bronx, approximately 57,900 customers between the Harlem River, 174th Street and 144th Street and Park Avenue were affected.

    In Manhattan, approximately 78,800 customers between Fifth Avenue and the East River, from 77th to 110th Streets were without power.

    Con Edison Chairman and CEO Kevin Burke said Wednesday night that the blackout was caused when breakers opened at an Astoria substation and cut off power to stations servicing Yorkville and parts of the Bronx.

    Why the breakers opened remains under investigation, but increased power demand due to the hot weather was not a factor, he said.

    The outage came a year after tens of thousands of Con Edison customers in Queens were affected by a blackout last summer.

    Last July, about 170,000 people in Astoria, Sunnyside, Woodside and Long Island City lost power for nine days during one of the hottest stretches of the summer.

    The state Public Service Commission issued a scathing report this year on last year's blackout, charging Con Edison's performance as "unacceptable and a gross disservice to its customers."

    Con Edison acknowledged that its performance last summer "was not up to the standards our customers have come to expect." But the utility said it was learning from that experience and "implementing many infrastructure improvements and new emergency response procedures."

    That includes a 1.4-billion-dollar investment to meet this year's summer power demand, including upgrades to substations and the distribution system.

    Meanwhile, heat and ozone advisories were in effect for the city Wednesday.

    With the heat advisory in effect, people are advised to avoid strenuous activity outside. Doctors also advise that people drink eight glasses of water a day and stay out of the sun to avoid heatstroke and dehydration.