The Commerce Department is expected to resume normal operations today after an electrical fire forced the closure of the main building yesterday to all but essential employees.

Repair crews restored full power and air conditioning to the Herbert C. Hoover Building at 1401 Constitution Ave. by 4:30 p.m. yesterday. Both systems were disrupted by a fire that began about 10:45 p.m. Monday in basement wiring, officials said.

Most of the 4,000 employees who work in the building were given the day off under excused administrative leave. About 150 "essential" workers, however, reported for duty, said Dan Nelson, a Commerce Department spokesman. Employees who "telework" from their homes or elsewhere were told to continue working unless the shutdown made it impossible to get their jobs done, Nelson said.

The department has a plan to ensure the continuation of essential services in the event of a terrorist strike or other disaster. Nelson said officials used a telephone tree to spread the word about the fire among key officials, but matters were not dire enough to move operations entirely, he said.

"We are not operating from a remote location; we are operating from Commerce," Nelson said yesterday. "Those that are operating here are the essential employees that would carry out the critical mission requirements of the Commerce Department."

The department released economic data as scheduled yesterday. The data showed that construction spending rose by 1.3 percent from March to April, to a seasonally adjusted annual rate of $970.4 billion, the highest level on record.

The Commerce Department is made up of 13 bureaus and agencies, including the Bureau of Economic Analysis, the Economics and Statistics Administration, the International Trade Administration, the Minority Business Development Agency and the National Oceanic and Atmospheric Administration.

The Hoover building also houses the National Aquarium of Washington, with 80 exhibits displaying 1,500 specimens of 250 kinds of animals. The fire disrupted power to 16 exhibits, forcing officials to run extension cords to unaffected parts of the building to restart the aerators used in some of the aquarium's tanks, said Bill Simpkins, executive director of the aquarium. Simpkins said that no animals died and that the extension cords were put in place within 11/2 hours of the power failure.

"The main concern is keeping air circulating through the water, since the fish do take their oxygen out of the water," Simpkins said. He said the aquarium plans to reopen today.

Some Commerce agencies were not directly affected by the closure, including the National Institute of Standards and Technology in Gaithersburg; the Census Bureau in Suitland; and the Patent and Trademark Office in Arlington. The 6,500 employees at the PTO's Arlington offices carried on business as usual yesterday, said Brigid Quinn, an agency spokeswoman. PTO officials who regularly coordinate with their counterparts at the main building -- those in legislative affairs, for example -- were able to continue their work, she said.

"It's safe to say that given Blackberrys and cell phones, that there was no effect on us," she said.

Michael E. Newman, a spokesman for the National Institute of Standards and Technology, said the agency's 2,800 employees reported for work yesterday. They could do everything except reach people in the Hoover building, he said.