Two months ago, a Bethesda woman who works for the National Institutes of Health learned that she wasn't getting a property tax break in South Florida that she wanted.

In response, the FBI says, she left a voice mail with the Broward County property appraiser claiming, "You guys now have anthrax spores once again."

Now, Michelle Ledgister finds herself charged with violating a federal law designed to fight terrorism and facing five years in prison and a $250,000 fine.

Federal agents arrested Ledgister on Monday in Rockville, and she is being held pending a hearing in Greenbelt today.

Ledgister holds an administrative job in NIH's Allergy and Infectious Disease division and does not have access to anthrax, NIH spokesman John Burklow said yesterday. He said he could not comment on her job status at NIH, where she has worked for about a year.

Ledgister, who owns a house in Parkland, Fla., had applied in Broward for a tax break given to full-time Florida residents. According to an affidavit filed in federal court by FBI Agent Ronald A. Gaskins, Broward officials sent Ledgister a letter June 8 telling her that her application had been denied because she wasn't a permanent resident.

She allegedly responded July 26 with a voice mail to the Broward property appraiser's office, the affidavit states. Ledgister identified herself by name. Then, according to the affidavit, she said: "I must commend your skillful sleuths in knowing where the main campus of NIH is located. But what they didn't tell you is that NIH is located where infectious agents are, and you guys now have anthrax spores once again, so do be careful. Toodles."

Two days after the phone message was left, a hazardous materials team searched the government office where the call was directed and found no evidence of anthrax, according to the affidavit.

Broward is not far from the Boca Raton, Fla., office building where three employees of American Media Inc. were infected in 2001 by an anthrax-tainted letter. One of the workers died. No one has been arrested in that case.

Ledgister, 43, said nothing during a brief detention hearing yesterday in U.S. District Court in Greenbelt.

U.S. Magistrate Judge William Connelly granted a request by Ledgister's defense attorney, Assistant Federal Public Defender Daniel Stiller, to delay the hearing a day.

Stiller told reporters that a federal magistrate judge in Florida recommended that Ledgister be released on a $10,000 secured bond and that an additional day was needed to have someone in South Florida file paperwork so Ledgister could put up her Florida home as collateral. Ledgister has agreed to go to Florida to face the charges.

Stiller said Ledgister is a law-abiding citizen. "She's humiliated."