The headquarters of the Internal Revenue Service, near the Mall in Northwest Washington, will remain closed for the rest of the week after a fire there Monday forced evacuation of the building.

The IRS said Tuesday that the fire in the basement of the building on Constitution Avenue affected the heating/ventilation/air conditioning system.

“We are working to restore service as soon as possible,” the IRS said in a statement.

The IRS said those employees who are ready for telework “are expected to telework from their approved location.”

The agency said many implies did work remotely Tuesday and will continue to do that for the rest of the week.

In addition, the IRS took pains to point out that the closing of the headquarters would not affect the processing of taxes.

“Taxpayers should continue to file their tax returns as they normally would,” the IRS said.

A fire in a transformer in the basement was reported about 3:30 p.m. Monday. That occurred after earlier difficulties with the HVAC system prompted officials to close the headquarters.

A few hundred people were still in the building when the fire was reported, and they were told to evacuate.

The imposing IRS building in the French Renaissance style is one of the structures that forms the federal triangle, near Constitution and Pennsylvania Avenues.

About 2,000 people work in the limestone and granite structure..