Ernesto strengthened into a hurricane Wednesday as it dropped torrential rain on Puerto Rico and left nearly half of all customers in the U.S. territory without power as it threatened to become a major storm en route to Bermuda. Schools and government agencies were closed in the U.S. and British Virgin Islands and Puerto Rico, where heavy flooding was reported in several areas, forcing officials to block roads, some of which were strewn with trees. More than 640,000 customers lost power in Puerto Rico, and 23 hospitals were operating on generators, officials said on Wednesday. They added that crews were assessing damage and it was too early to tell when electricity would be restored. More than 140 flights were also canceled to and from Puerto Rico. Flash flood warnings remained up because of continuing rain. In the north coastal town of Toa Baja, which is prone to flooding, dozens of residents moved their cars to higher areas. Ernesto, a Category 1 hurricane, was gradually strengthening and could become a Category 3 hurricane by Friday. Its center was expected to pass near Bermuda on Saturday. Between 3 and 6 inches of rain was forecast, with more possible in isolated places. Forecasters also warned of heavy swells along the U.S. East Coast. The storm was over open water about 675 miles (1,085 kilometers) south-southwest of Bermuda early Thursday, with maximum sustained winds of 85 mph (140 kph) and moving northwest at 16 mph (26 kph). Ernesto is the fifth named storm and the third hurricane of this year’s Atlantic hurricane season