WASHINGTON — Hundreds of businesses and malls in this area and along the Northeast corridor were forced to shut down Wednesday, after mid-Atlantic utilities sent an urgent plea to conserve energy to “prevent widespread, uncontrollable outages in the region.”

“This is widespread and very serious,” said a spokeswoman at Pepco, the D.C.-based utility, one of the power companies that issued the plea. Service disruptions, affected 20 million to 30 million people in most of Pennsylvania, all of Delaware, parts of New Jersey, Maryland and Virginia and all of Washington. The crisis is expected to continue through Thursday.

In this area, regional malls, including Montgomery Mall in Bethesda, Md.; Fashion Centre in Pentagon City, Arlington, Va., and Tysons Corner Center in McLean, Va., were forced to close at dark, with some experiencing blackouts during the day, causing computer systems to break down and cash registers to stop abruptly.

Washington’s downtown district as well as Silver Spring, Md., and downtown Bethesda, however, were not affected.

Some, like Pentagon City, anchored by Nordstrom and Macy’s, dimmed the lights and turned off the fountains, as well as all 14 escalators and 11 elevators to conserve energy throughout the day.

“We are trying to be concerned good neighbors, though some of our customers are complaining about walking up the stairs,” said Lowel Davis, the mall’s operations director. “There are also some other issues like liability. We don’t want people falling down on the ice because they can’t see where they’re going.”

Tysons Corner Center had closed early at 6:30 p.m. on Tuesday night because of icy conditions and closed at 5:30 p.m. Wednesday night. Usual closing time is 9:30 p.m.

Nordstrom, which operates in Pentagon City and Tysons Corner Center, gave flashlights to its customers after blackouts occurred.

“We are just doing what we need to do,” a spokeswoman said.

A spokeswoman at Public Service Electric & Gas, a New Jersey power company, said it was cutting or diminishing electricity in one-hour intervals in various New Jersey communities because of a drain on its system.

Spokesmen at four regional malls in northern and central New Jersey — Paramus Park in Paramus, Willowbrook Mall in Wayne, Monmouth Mall in Eatontown and Menlo Park Mall in Menlo Park — said they had not been affected by power failures Wednesday and planned to keep regular hours, closing at 9:30 p.m.