Residents should expect to spend several days without power as a result of Hurricane Irene, officials say. “I urge customers to prepare for possible extended outages,” said Thomas Graham, Pepco’s regional president.

With more than 788,000 customers in the District of Columbia and Montgomery and Prince George’s counties, Pepco has asked other electric company to send 600 utility workers to help, as well as 330 tree crews from the Asplundh Tree Expert Co. in Pennsylvania. As of Thursday, 150 employees of First Energy in Ohio had already arrived.