In response to initial tests showing anthrax contamination in two Defense Department mailrooms, the U.S. Postal Service has shuttered the facility that processes government mail, temporarily halting delivery to all D.C.-area federal agencies, including Capitol Hill.

Congressional officials said Tuesday, however, that mail delivery to House and Senate offices will remain on schedule, and they sought to assure employees that the parcels are safe.

“For the next two days, mail already delivered by the USPS and cleared by the vigorous testing methods applied by the House’s mail screening process will be delivered to House offices,” House Chief Administrative Officer Jay Eagen wrote to lawmakers and staff today.

An aide to Senate Sergeant-at-Arms Bill Pickle made a similar statement: “The Senate has a thorough and sophisticated mail processing system in place. Any mail delays or suspension would be as a result of the U.S. Postal Service authorities doing so until final testing is completed at the Pentagon.”

The delivery of newspapers, packages from carriers other than the post office, “Dear Colleague” letters and other inside mail will likewise continue on schedule, Eagen wrote.

House officials noted, however, that if mail facilities remain closed, delivery to Capitol Hill could be affected beginning Thursday, along with other government offices that receive mail from the USPS’ V Street Northeast facility.

Although mail addressed to Congress is irradiated by the USPS and tested for a variety of substances, both the House and Senate utilize extensive mail screening procedures at separate off-site facilities. This causes a short delay in delivery to Capitol Hill.

A senior House aide added that in addition to mail received Friday and Monday, the chamber’s off-site mail processing plant has also been tested for anthrax contamination.

D.C. Del. Eleanor Holmes Norton (D) called for a hearing on the preliminary test results Tuesday in a letter to Government Reform Chairman Tom Davis (R-Va.).

“We need to know what we can now about the source of the substances and the outstanding flaws in a system on which the federal government has spent billions of dollars to enable detection of anthrax contamination before reaching a mail facility in this area,” wrote Norton, who asked for the hearing to take place before April 5.

“This is a serious issue that warrants serious attention from Congress, and he will carefully consider Mrs. Norton’s request,” a Davis spokesman said.