Anthrax found at Lake Worth, Fla., post office.(Knight Ridder Newspapers)

MIAMI _ Palm Beach County authorities Thursday confirmed a new anthrax discovery at a Lake Worth post office that served as the "dead letter" office and delivery site for the old Lantana address for the National Enquirer and other American Media Inc. tabloids.

The discovery brings to six the number of Palm Beach County post offices that have tested positive for anthrax.

Tim O'Connor, spokesman for the Palm Beach County health department, said a single anthrax spore was found in a manual mail sorting area at the Lucerne Avenue post office in Lake Worth. No people were infected, he said.

Environmental Protection Agency cleanup crews, armed with heavy duty bleach, were slated to disinfect the area overnight and the post office should reopen Friday.

Officials are making antibiotics available to any of the 48 postal workers at the Lake Worth branch, even though no one is showing any symptoms and the amounts of anthrax found have been minimal.

Postal authorities believe one parcel dumped spores at all six postal facilities, that parcel was eventually delivered to AMI and infected Sun photo editor Bob Stevens, who died of inhalation anthrax.

The Miami chapter of the American Postal Workers Union strongly questions this scenario. Although union bosses have no proof, they allege more than one parcel coated with anthrax could have left spores at so many postal facilities.