Tests have confirmed that anthrax inhalation was the cause of death of two postal employees who worked at a facility that processes mail for the city, including the U.S. Capitol complex. Meanwhile, an anthrax culture was found in a remote mail delivery site for the White House.

White House spokesman Ari Fleischer says the site where the anthrax culture was found is a military facility several kilometers from the White House and investigators are probing the matter. He says the White House itself has tested negative for the potentially deadly bacteria.

The announcement came shortly after Washington Mayor Anthony Williams confirmed that two employees at the Brentwood postal facility died of anthrax inhalation. That facility handled an anthrax-laced letter sent to Senate Majority Leader Tom Daschle.

Two other employees at the postal office have come down with inhaled anthrax and are being treated. A mail handler in New Jersey, where the tainted letter to Senator Daschle was mailed, is also believed to be suffering from the disease.

All workers at the Brentwood facility are getting antibiotics but had been told by authorities last week they were not at risk and did not need to take the drugs.

U.S. Health and Human Services Secretary Tommy Thompson promised to act faster to protect people from the threat. "We will not only immediately begin testing and treatment at the site where the letter was received, but we will simultaneously begin testing and treatment at all postal facilities throughout which that letter may have passed," he said. "We will make medicine immediately available to those employees who may have been at risk of exposure."

Secretary Thompson spoke at a congressional hearing that was held at his Washington headquarters because congressional office buildings remained closed Tuesday to sweep for anthrax contamination.

Twenty-eight congressional staffers have tested positive for anthrax exposure after the bacteria-tainted letter was opened in Senator Daschle's office last week.

Federal Bureau of Investigation officials are probing a number of cases linked to the bacteria, including the death of a tabloid newspaper employee in Florida earlier this month.

U.S. Attorney General John Ashcroft told reporters he is not able to say whether the anthrax incidents are linked to last month's terrorist attacks on the World Trade Center and Pentagon. "We believe these to be terrorist acts," he said. "We are not able to rule out an association with the terrorist acts of September 11, but neither are we able to draw a conclusive link at this time in that respect."

Thousands of people have been tested for anthrax exposure, most of them workers on Capitol Hill.