WASHINGTON?Federal investigators pressed for evidence at research labs and universities that may have access to anthrax and questioned pharmacies to see if anyone tried to buy large amounts of antibiotics before the nationwide anthrax scare.

As a third television network in New York reported an anthrax exposure and a New Jersey postal worker who may have handled two anthrax letters tested positive for the disease, authorities offered $1 million for information leading to the arrest of those who sent the deadly spores.

?Once again, we call upon the public to assist us in this fight against terrorism,? FBI Director Robert Mueller said in a joint announcement with Postmaster General Jack Potter.

One possible scenario is someone living in the United States might have worked with an overseas domestic terrorist group with enhanced biochemical capabilities, officials said.

?We think it may be ill advised to think about the situation in terms of an either/or matrix,? Attorney General John Ashcroft said.