Trying to reassure postal workers and an anxious public, the postmaster general moved to shore up the U.S. postal system against biological attack -- even suggesting that people should wash their hands after touching their mail.

"We're telling people that there is a threat -- that right now the threat is in the mail," Postmaster General John E. Potter said in television appearances yesterday. "There are no guarantees that mail is safe."

The Postal Service plans to begin installing germ-killing machines by Nov. 1, he said. To protect its 800,000 workers, the agency will hand out gloves and masks, switch from air guns to vacuum machine cleaning tools to prevent the spread of deadly germs around work areas, and use more potent antibacterial cleaning solutions.

As a precaution, some postal facilities in Maryland, Virginia and New Jersey will be tested for anthrax, the agency said yesterday, including the Baltimore main branch and post offices in Frederick, Gaithersburg and Waldorf. Set to begin today, the testing is being done because those stations receive mail from facilities in Washington and New Jersey where the bacteria have been found.

Stung by criticism over their response to the anthrax attacks that have sickened a few Americans but frightened many more, federal officials scrambled to strengthen the nation's defenses against bioterrorism.

The government announced a deal with the maker of anthrax-fighting drug Cipro to supply enough of the antibiotic for 12 million people by Jan. 1.

No new confirmed anthrax infections surfaced yesterday. Doctors are monitoring about 30 people hospitalized in the Washington region, including two at the Greater Baltimore Medical Center in Towson and another last night, because of skin lesions, at Johns Hopkins Hospital. Health officials say they don't expect all those illnesses to be diagnosed as anthrax.

"We're investigating a lot of cases," said Ivan Walks, Washington's chief health officer, in a television interview last night. "But we want every case that is suspected to be reported."

Yesterday, investigators from the Centers for Disease Control and Prevention continued their sweep of the Brentwood Central Mail Facility in Washington, where anthrax spores have turned up in numerous areas.

Investigators believe the building was contaminated by a letter that passed through the sorting center on its way from Trenton, N.J., to Senate Majority Leader Tom Daschle earlier this month. The letter was among the suspected mail attacks in the past month that have claimed three lives, sickened at least nine other Americans and forced thousands more to swallow a daily regimen of antibiotics.

The trail of contamination extended to an off-site White House mail screening station, where trace amounts of anthrax were found Tuesday. Preliminary tests of 120 workers at the White House mail room and the screening station, at Bolling Air Force Base, came back negative for the disease, White House spokesman Ari Fleischer said yesterday.

All mail headed to the White House has been held at an off-site mail center since Oct. 11.

The U.S. Postal Service advised people who worked in mailrooms at institutions that receive bulk mail from the Brentwood facility to get antibiotics at D.C. General Hospital.

Such institutions include the Library of Congress, the Georgetown University Law Library and the Humane Society. The recommendation extends to about 200 employees.

In announcing the new safeguards for the postal service yesterday, Potter provided few details about the proposed germ-killing technology. He said only that the machines would be expensive and that the agency has set aside $200 million to purchase or lease the new equipment.

"This new technology won't be cheap, but we are committed to spending what it takes to make the mail safe," Potter said.

Several kinds of radiation could be used to sterilize mail, experts said yesterday, including gamma rays and X-rays. But industry experts said the most practical choice might be electron-beam radiation, which is generally faster than the other two technologies.

Titan Corp. of San Diego, which makes an electron-beam sanitizer used in the food industry called SureBeam, says its equipment has been proven to kill anthrax spores and can sterilize 18,000 kilograms of ground beef in a few seconds.

If high-volume equipment were set up at postal facilities, it would cost about 1 cent per letter to sterilize mail, the company says.