Portland State University is investigating a tenured professor of economics who is reported to have accused a student during class of being an FBI informant and selling weapons to other members of the class.
Students in the class say the professor, John B. Hall, stopped teaching in the middle of a lecture on January 14.
According to their accounts, Mr. Hall said an FBI informant was in the room and pointed at one of their classmates, Zaki Bucharest.
Mr. Hall then went on to say that Mr. Bucharest had served as a sniper in the Israeli army, tried to sell weapons to members of the class, and worked with the FBI, among other claims, the students said. Mr. Hall also showed students a letter he had written to the FBI.
"His voice was in a totally normal tone," said Brett Condron, a student in the class. "It was just like he was lecturing on."
Students say Mr. Bucharest, who is chief of staff for the university's student government, stayed silent while the professor talked. When Mr. Hall finished speaking, Mr. Bucharest stood and told the class that it was true that he had been a sniper in the Israeli army, but that Mr. Hall was wrong about other things. He then left.
"I expected that Zak was in on the joke and would scream, 'Psych,'" said another student, Jeremy Veysseire.
Mr. Hall could not be reached by phone or e-mail for comment on Thursday.
In a letter to the university's student-run newspaper, the Vanguard, Mr. Hall wrote that, based upon his students' reports, "I cannot help but to think that the process currently is being shaped in order to end my tenure at PSU."
"I decided to take a stand," he said in the letter. "I observed the situation becoming extremely dangerous, not only for me but for about eight of my very finest students. I felt that what I had to do should not have been my responsibility."
A university spokesman, Scott Gallagher, said a student has filed a complaint against Mr. Hall, but the spokesman could not give any details. He said Mr. Hall has been relieved of his teaching duties and an investigation is under way; no disciplinary action has been taken so far.
The university said it had no record of any complaints being filed about Mr. Bucharest.
A new professor has been brought in to teach Mr. Hall's class, and students have been encouraged to go to the university's office of public safety if they have any concerns about their well-being.
Mr. Bucharest's lawyer, Elden Rosenthal, declined to comment beyond issuing a statement in which his client stated: "I have never been affiliated with the FBI in any way, and I have never been an informant. I have never in any way done anything to incite violence at PSU. I have admired Professor Hall since I first took a class from him and cannot imagine what I did or said to cause him to treat me the way he did."
The Vanguard first reported the story on Wednesday. Its Web site crashed at one point because of high traffic the story drew, said Sarah J. Christensen, the editor in chief.
"It's just a very confusing situation," Ms. Christensen said. "I think that's what's so interesting. It's a whodunit."