Rain, sleet, snow and hail couldn't do it. But anthrax — and a lawsuit — might be the one thing that finally shuts down the United States Post Office, at least in New York.

Lawyers for the union of postal employees late Monday filed suit in Manhattan federal court seeking to force the postal service to close a huge mail-sorting facility in New York City.

"Lawsuits are for when things break down," said Louis Nikolaidis, a lawyer for the New York Metro Area Postal Union. "Obviously we have a situation with anthrax where things have broken down."

The lawsuit claims that the U.S. Postal Service engaged in the storage and transportation of hazardous substances without a permit. The suit aims to close and test the nine-story, 2-million-square-foot Morgan Processing and Distribution Center.

"We're simply asking the post office to close the building. If that's not done, we shouldn't be in that building," union President William Smith said.

The suit comes as absenteeism at the facility has reached 30 percent and 12 postal workers in Manhattan have been referred to dermatologists to check symptoms that might be anthrax-related.

The symptoms were spotted while the Postal Service was screening and dispensing precautionary antibiotics to 7,078 employees, according to Dr. Tom Matte of the Centers for Disease Control and Prevention. He said the symptoms "did not look highly suspicious" and the referrals were based on "an extremely low threshold."

Matte said biopsies have been performed on four of the workers but results are not in yet.

No postal workers in New York have come down with anthrax. Inhalation anthrax has killed three people outside New York, including two Washington, D.C., postal workers. New York City has four confirmed and two suspected skin anthrax cases, all linked to news media outlets.

David Solomon, regional vice president for operations for the Postal Service, said medical experts had told the Postal Service that the contamination on the Morgan building's third floor could be safely blocked off.

Besides the four optical ZIP code sorting machines that tested positive for anthrax in the building, 22 other machines on the third floor and an unspecified number on the second floor were to be cleaned beginning Monday with a high-efficiency particle arresting vacuum and a bleach solution, Matte said. The machines have been cordoned off since the test results came back.

In addition, the entire third floor will be HEPA-vacuumed. The Postal Service also announced that environmental testing would be done at the main processing stations for Brooklyn and Queens and Nassau and Westchester counties.

"If they tell us there is a danger to the safety of our employees we will close it down," he said.

A 53-year-old Morgan worker who died Oct. 10 did not have anthrax, the medical examiner's office said Monday.

And a Postal Service executive, standing before a 7-foot medallion of a Pony Express rider, said that despite it all, there have been only "minor, minor disruptions" of mail delivery.

Postal Service spokeswoman Pat McGovern said the Morgan facility handles 12.5 million pieces of mail a day. There are 20 million pieces of mail delivered in the city each day, McGovern said.

The Associated Press contributed to this report.