Preliminary tests on two mailbags in the U.S. embassy in Vilnius, Lithuania, have shown up positive for the presence of anthrax, a State Department spokesman said Wednesday. 

It is the second discovery of an embassy contamination this week.  The first case was in Lima, Peru, on Monday.

Spokesman Richard Boucher said final laboratory results could be available by the end of the week. 

Boucher said all State Department employees who handle mail, including those at a contaminated site in suburban Virginia, are being treated with a 60-day regimen of antibiotics.  The embassy mailroom has been sealed. 

The disclosure came after the head of the State Department's medical unit said the two-block building in Washington is safe despite the probable presence of low concentrations of anthrax spores "all over the place." 

"We've got envelopes probably throughout the system that may have very few ... spores on them. But they are probably all over the place," said Dr. Cedric Dumont. "We need to go back and have a reality check on the level of risk. 

Dumont spoke to a large gathering of department employees Tuesday about the threat of infection. Angry workers at the "town hall" meeting blasted the department after officials reversed their decision to resume testing in the main building instead of ending the tests and just cleaning the mailrooms.

"Your office areas probably have some contamination," Dumont said with a caveat.  "What we're telling you is that an envelope with a couple of spores is not going to give you inhalational anthrax. It may -- very low probability -- cause cutaneous anthrax," the less severe form of the illness. 

Department officials decided to resume testing after complaints from employees dissatisfied by official statements that there is no indication the anthrax spores have spread beyond the mailrooms.

Employees told officials they were not comfortable with the fact that anthrax has been found in mailrooms on two floors.

One participant at the meeting requested at least a random sampling of employees throughout the building to determine whether risks were limited to the mailrooms. Another suggested anthrax spores may have been carried from the mailrooms to other State Department offices on clothing or floated elsewhere through the air. 

Boucher admitted the reversal came only after the public session and wasn't necessarily based on science. 

He said there will now be a series of six public information meetings in the department to try to answer questions of concerned workers.

Fox News' Teri Schultz and the Associated Press contributed to this report.