WASHINGTON, Oct 19: The number of positive exposures to anthrax dropped by at least one on Capitol Hill on Friday as officials checking the area for the bacteria declared two buildings a “warm zone” where protective clothing must be worn.

Only a few senators and their aides wandered the eerily quiet halls of Congress, where the chambers of the Senate and the House of Representatives were shut while an anthrax “sweep” was conducted by hazaradous material experts and police.

Historians said the legislative interruption was unprecedented, although business was halted on Sept. 11 after the attacks on New York and Washington.

The suspension of congressional business resulted from the discovery of anthrax in a letter opened in Senate Majority leader Tom Daschle’s office on Monday.

But after days of anxiety, one senior senator had a nugget of good news. “We are down to 30 positive exposures,” said Assistant Senate Majority leader Harry Reid, Democrat of Nevada. “One was a false positive.”

Following similar anthrax cases in Florida and New York, the Capitol exposures deepened concern over a biological attack among Americans, who have been on edge since the hijack attacks killed nearly 5,400 people.

As a sweep for anthrax continued in the Capitol and House and Senate office buildings, Capitol police said two buildings where anthrax had already been detected earlier this week were now off-limits to anyone not wearing special protective gear.

A memo addressed to Capitol police watch commanders said the Hart building, where Daschle’s office was located, and the Dirksen building, where officials later found anthrax bacteria in a basement mail room, would be considered a “warm zone.”—Reuters