WASHINGTON - Federal agents have been following a former professor turned in by his family as a possible suspect in the Unabomber killings, and they prepared yesterday to search his Montana home, federal law enforcement officials said.

The man under suspicion was described as a Harvard graduate and a former professor at the University of California at Berkeley, according to one federal official, who requested anonymity.

A second federal law enforcement official said the man has been under surveillance for ''a short period of time.'' The search was set to take place at the man's home in Lincoln, Mont., the second official said.

''We like the looks of this guy as the Unabomber, but we don't have make or break evidence yet,'' the first official said. ''We have some writings that match up, but we don't have his tools yet. We want the irrefutable motherload of evidence.''

Members of the man's family found some old writings of his while cleaning out a place where he once lived, and the writings raised their suspicions, this official said. They approached an attorney in Washington, who called the FBI, to alert the bureau. Federal agents later got consent to search the former residence, this official said.

The FBI has spread copies of the Unabomber's writings throughout the academic community in hopes of finding someone who recognizes the work.

Last September, the New York Times and the Washington Post published, in the Post, his 35,000-word treatise on the inhumanity of industrial society after he promised to stop planting bombs that kill people.

The attention of investigators was drawn to him after his family approached federal officials with their own suspicions about his role in the Unabomber's 17-year bombing spree, one official said.

The Montana Justice Department said a closure order, signed by an FBI agent, had been issued for airspace within five-mile radius of Lincoln, Mont.

CBS News said the initial report about the man came earlier this year from an attorney who approached the FBI on behalf of a man who suspected that the Unabomber might be his brother.

FBI has been hunting the Unabomber since 1978.

The first Unabomber incident occurred at Northwestern University outside Chicago in 1978. Three people have died and 23 more were injured in 15 subsequent Unabomber attacks; the most recent was April 25, 1995, when a timber industry executive was killed.

For three years, a San Francisco-based task force of two dozen agents from the FBI, Treasury Department and Post Office has pored over travel records, tips, interviews, lab results and case records searching for clues.