State and fire department officials said tests by the Army National Guard and state health officials found no signs of any biotoxin. Samples will be sent to the Centers for Disease Control and Prevention for review.
Nearly 100 people were cleared from the building after the powder was found about 12:45 a.m. on a table where mail is processed, fire Capt. Jolene Davis said. The center reopened Tuesday evening.
There was a similar scare later Tuesday morning at a Postal Service distribution center in Tukwila, just south of Seattle. Tests on a granular substance found in a mail basket there were negative, said Jeff Scobba, a U.S. Postal Inspection Service spokesman.
Elsewhere, six Postal Service workers were taken to a hospital in Fort Myers, Fla., after they were exposed to an unknown white powder when they opened a mail container unloaded from a FedEx plane at Southwest Florida International Airport.
Gerry McKiernan, a spokesman for the U.S. Postal Service in Washington, said Tuesday night that tests on the substance found there also were negative.
Since 2001, when anthrax attacks killed five people and briefly paralyzed Capitol Hill, finds of white powder have triggered evacuations and rapid tests.
In January, a single letter addressed to Federal Reserve Vice Chairman Roger Ferguson tested positive for anthrax. Later, more detailed readings showed no sign of the germs. The Postal Service says no anthrax was found at a government mail facility through which the letter had traveled.
No one has been charged in the 2001 attacks, which have been linked to a strain of anthrax used at a U.S. government lab. Federal investigators searched a former apartment of a microbiologist who once worked at the lab, Steven Hatfill, but never stated publicly that he was a suspect. Hatfill has denied involvement.
In December, the FBI confirmed it was investigating a site on public land in Frederick, Md. in relation to the anthrax scare, CBS News Correspondent Jim Stewart reported. Sources said the search was in connection with the investigation into Hatfill.
The anthrax attacks raised public alarm over the prospects for bioterrorism.
In his State of the Union speech in January, President Bush called for nearly $6 billion to make vaccines and treatments against potential bioterror pathogens.
The National Institutes of Health bioterrorism budget, meanwhile, has increased 500 percent this year to $1.3 billion.