The anthrax mailings probably are the work of a man who is familiar with hazardous material, works where he has little contact with other people and may have held a grudge against letters' addressees, the FBI said Friday.

In a fresh appeal to the public for help in solving the anthrax mailings, FBI officials released a profile of the suspected mailer developed by the agency's behavioral experts.

The profile does not address the question of whether the person is foreign or from the United States.

FBI officials said the person may work in a laboratory and "is apparently comfortable working with extremely hazardous material. He probably has a scientific background to some extent, or at least a strong interest in science."

The person "did not select his victims randomly," making the effort to find a correct address and zip code of each victim and ensuring that the proper postage was used.

NBC, the New York Post and Sen. Tom Daschle were selected, the FBI said, because "these targets are probably very important to the offender. They may have been the focus of previous expressions of contempt which may have been communicated to others or observed by others."

The person who mailed the letters "lacks the personal skills necessary to confront others," the FBI said, suggesting that the man may have held a grudge against the targets for a long time.

After the Sept. 11 hijacker attacks, FBI officials said the person may have become more secretive and changed his usual pattern of activity.

"He may have displayed a passive disinterest in the events which otherwise captivated the nation," the FBI said. "He also may have started taking antibiotics unexpectedly."

During the course of the anthrax mailings and intense media coverage, the man may have altered his physical appearance, displayed pronounced anxiety or noticeable mood swings, and may have appeared more withdrawn or unusually preoccupied, the profile said.