WASHINGTON (AP) A letter sent to Senate Majority Leader Tom Daschle tested positive for anthrax yesterday as the bioterrorism scare rattling the nation reached the halls of Congress.

The discovery of anthrax in Washington followed earlier instances in Florida, New York and Nevada in which at least 12 people were exposed to spores of the potentially deadly bacteria. Monday night, another case of the disease was announced in New York.

The 7-month-old child of an ABC News employee has tested positive for anthrax, ABC News President David Westin said. The child is expected to recover. New York police commissioner Bernard Kerik said news agencies throughout the city were being inspected for anthrax contamination.

The piece of mail in Daschle"s office, which contained a powdery substance, was dispatched to an Army medical research facility at Fort Detrick, Md., for further examination, said Capitol Police Lt. Dan Nichols.

The Fort Detrick findings could be available as early as today, officials said. Nichols and others warned that the initial tests were not necessarily accurate.

Bush told reporters "there may be some possible link" between the spate of anthrax incidents across the country and Osama bin Laden, who administration officials say was behind the Sept. 11 airline hijack attacks.

"I wouldn"t put it past him, but we don"t have any hard evidence," Bush said.

Daschle was in the Capitol and was not exposed to the letter, which was opened in his other office a block away in the Hart Senate Office Building. Officials would not identify the person who opened the letter, though Nichols referred to the aide as a female. Aides who may have been exposed to the letter were tested with nasal swabs and being treated with the antibiotic Cipro as a precaution, said Dr. John Eisold, attending physician in the Capitol.

"They are innocent people caught up in a matter for which they have nothing to do," a somber-looking Daschle (D-S.D.) told reporters at a news conference outside the Capitol. "I am very, very disappointed and angered."

Nichols said a criminal investigation led by the FBI was under way.

The Daschle letter and similar scares in other congressional offices prompted a halt to all mail deliveries in the Capitol and raised the angst there. Many lawmakers, aides and other employees already were nervous about working in a building that could be a high-profile target for terrorists.

In Trenton, N.J., Postal Inspector Tony Esposito and FBI officials said the letter to Daschle was postmarked in Trenton on Sept. 18, the same date and postmark on a letter that infected an NBC employee in New York last week.