WASHINGTON (AP) _ The FBI and Justice Department are investigating charges by an FBI agent that colleagues in the agency's crime laboratory have slanted testimony and fabricated evidence in high-profile trials, the FBI said Monday.

But in a statement, the FBI said after reviewing the laboratory work in more than 250 cases it has found no evidence that to support the allegations raised by Special Agent Frederic J. Whitehurst.

In an interview Wednesday night on ABC's ``Primetime Live'' program, Whitehurst, a 13-year veteran of the crime lab with a doctorate in chemistry, called the FBI's statement ``garbage.''

``I'm obviously disagreeing with my superiors in these matters,'' Whitehurst said. ``I believe there has been evidence tampering. I personally know abut the review of those 250 cases. The report is garbage.''

Whitehurst's allegations arose Wednesday after defense attorneys for O.J. Simpson said they wanted to call him as a witness. Whitehurst has accused an FBI colleague who was a prosecution witness in Simpson's trail of misconduct in other cases.

The FBI said in its statement that Whitehurst for several years has been raising ``a variety of concerns about forensic protocols and procedures'' at the agency's laboratory.

``In all instances, the FBI, or the Department of Justice inspector general's office, or, in some cases, both, have vigorously investigating his concerns and are continuing to do so,'' the FBI statement said.

Whitehurst testified last month at another trial that he himself was pressured to distort findings about the World Trade Center bombing to favor prosecutors.

Citing a series of internal memos sent by Whitehurst to his FBI supervisors, ABC News said Wednesday that the agent listed ``one example after another of what he calls perjury, fraud, even the fabrication of evidence'' in cases at the FBI crime lab going back at least five years.

One of the cases, ABC said, involved the 1991 Georgia bombing case that was investigated by now-FBI director Louis Freeh. Walter LeRoy Moody Jr. was convicted in the mail-bombing deaths of a federal judge and a civil rights lawyer.

ABC said Whitehurst alleges that two agents in that case slanted evidence by testifying about tests that weren't done and scientific conclusions they couldn't support.

One of the two agents, ABC said, was Roger Martz, who gave damaging testimony against Simpson after he was called by the defense and declared a hostile witness.

Martz could not be reached for comment. There was no answer at their Washington office phones late Wednesday and neither men had home phone numbers listed in the Washington area.

The FBI lab was used to analyze some blood evidence involving Simpson. Martz, a toxicologist, testified at the Los Angeles trial that blood on a sock from Simpson's bedroom and from the crime scene showed only vague signs of a preservative. Simpson's lawyers say the blood was planted and the presence of the preservative proved it.

Whitehurst's testimony about being pressured to change his own findings was delivered last month in the terrorism trial of Sheik Omar Abdel-Rahman and nine other Muslims accused of plotting to bomb the United Nations and other New York City landmarks.

While testifying Aug. 14, Whitehurst said Martz was among several FBI investigators who concluded the World Trade Center bomb was urea-nitrate based even though it was impossible to prove that scientifically because the substance is so common.

After Whitehurst complained to his superiors, Whitehurst said, reports about the bomb were corrected. He said they were accurate when they were introduced at last year's World Trade Center trial, which resulted in convictions for followers of Abdel-Rahman.

At the terror conspiracy trial, Whitehurst said when he first told his supervisor about the errors, the supervisor ``became extremely loud and extremely angry. ... He advised us that he would now have to embarrass his chemistry toxicology unit chief and that we were never, ever again to do something like that to him.''

Later, he said, the supervisor told him he had been instructed by his bosses to have Whitehurst change his reports and debates within the FBI about the evidence continued throughout the year.

Terror trial defense lawyer Valerie Amsterdam asked him if changing the report would support a theory of guilt against those charged in the 1993 trade center bombing that killed six people and injured more than 1,000 others.

``I was at times left with that impression. There was a great deal of pressure upon me to bias my interpretation of the data ... in support of the presence of urea nitrate and other things that would have supported a theory of guilt,'' he said.

He said that after he was confronted by a fellow FBI agent at a Christmas party in late 1993, he complained to the Justice Department's Inspector General's Office, which is continuing to investigate.

Whitehurst, the FBI's main explosives-residue analyst at the time of the bombing, said he has since been demoted and assigned to analyze paint for forensic evidence.

Closing arguments have been going on this week in the Abdel-Rahman trial.