SYRACUSE, N.Y. (AP) _ Two Harvard University computer experts appeared Wednesday before a federal grand jury that is investigating the origin of a computer virus that jammed a nationwide network of computers.

The investigation is focused on Cornell University graduate student Robert Morris Jr., 23, of Arnold, Md., who authorities believe created the virus.

The virus program transmitted copies of itself from computer to computer, cramming an estimated 6,000 computers nationwide. It caused at least $97 million in damage, because of interrupted work on computers that had to be shut down, and in the work needed to resuscitate the computers, according to the Computer Virus Industry Association.

FBI agents in Massachusetts last week subpoenaed three people at Harvard, where Morris was a computer science undergraduate until June.

Two of them, graduate student Paul Graham and computer programmer Andrew H. Suddeth, appeared Wednesday afternoon before the grand jury.

Suddeth has said that Morris called him in a panic to get help in getting out a message to other computer operators after he realized what the virus was doing.

Suddeth on Tuesday said he wanted to stop commenting publicly until he had appeared before the grand jury.

The third person subpoenaed, Mark Friedell, an associate professor of computer science at Harvard, was excused from testifying. He said he told prosecutors he knew nothing of Morris' alleged involvement with the virus.

Friedell was an adviser to Morris when Morris researched and wrote an undergraduate thesis about computers.

A week ago, federal agents seized computer tapes from files Morris had at Harvard. The files, which are accessible to computers located off the Harvard campus, were created and edited a week before the virus clogged the network.

On Nov. 10, FBI agents in Ithaca executed two other search warrants at Cornell, seizing computer tapes and notes that agents believe are linked to the creation of the virus.

Morris' lawyer, Thomas Guidoboni of Washington, told the newspaper that Morris has not been subpoenaed to appear before the grand jury in Syracuse.

Guidoboni so far has advised Morris not to talk with anyone about the virus, including FBI agents. However, the lawyer said an agreement may soon be reached in which an interview with agents would be arranged.

Guidoboni said he was uncertain where Morris would be interviewed.

''I think the FBI would like to talk with him,'' Guidoboni said. ''But I'm not aware specifically what they'd like to talk to him about.''