WASHINGTON (Reuters) - Federal agencies in the Washington area will be open on Monday following a brush with Hurricane Irene over the weekend, the Office of Personnel Management said on Sunday.

Tens of thousands of federal employees have the option to take unscheduled time-off or work from home, the agency said, adding that some federal buildings could still be without power on Monday.

As many 3.6 million homes and businesses on the East Coast of the United States lost electricity as Hurricane Irene swept through the region over the weekend, causing at least 20 deaths and widespread flooding.

(Reporting by JoAnne Allen; editing by Anthony Boadle)