Indiana University fired computer science professor XiaoFeng Wang on the same day that FBI agents executed search warrants at two homes owned by Wang and his wife, his union revealed Monday as it asked the school to revoke his termination.

The Bloomington chapter of the American Association of University Professors in a letter to Indiana U. on Monday protested Wang's firing, which it said occurred without the "highest level of scrutiny and process" required by university policy.

The letter came as both the FBI and the university declined to reveal what led to the search of Wang's home and the termination of the tenured professor after two decades at the university.

Indiana U. spokesman Mark Bode, in an email to CNBC, said, "Indiana University was recently made aware of a federal investigation of an Indiana University faculty member."

"At the direction of the FBI, Indiana University will not make any public comments regarding this investigation," Bode said. In accordance with Indiana University practices, Indiana University will also not make any public comments regarding the status of this individual."

The university has removed the online profiles of both Wang, who researched cryptography, privacy and cybersecurity at the university's Luddy School of Informatics, Computing and Engineering, and his wife Nianli Ma, a systems analyst and programmer in the university's library division.

Indiana U. Law Professor Alex Tanford, the union chapter's president, told CNBC in an interview Monday that Wang contacted him earlier this month as the university conducted what had first appeared to be a "routine" investigation over a grant application and how he reported a publication of his curriculum vitae.

Wang, who had been barred from his office and from access to his computer during the university's probe, emailed Tanford on Friday to say, "I've been terminated," the law professor recalled.

The email arrived shortly after Tanford heard from his daughter, who lives out of state, asking him what he knew about news reports of the FBI searching a house that same day in Bloomington, where Indiana U. is located.

That house is owned by Wang and Ma.

In addition to the Bloomington house, FBI agents at the same time Friday were searching and seizing materials from a second home owned by the couple, in Carmel, Indiana, located about 70 miles northeast of the university.

Tanford said a termination letter to Wang on Friday did not say why he was being fired after more than two decades at the school.

Tanford accused the university of "hypocrisy" for not following its own policy in terminating Wang, which Tanford said was "totally unnecessary," since the school could have continued its effective suspension of the computer science professor.

"It is our understanding that Professor Wang was not provided the due process specified" by university policy, the union chapter's executive committee said in its letter to Indiana U. Provost Rahul Shrivastav.

"His appointment was terminated without the required notice and a hearing before the Faculty Board of Review."

"We are aware of news reports indicating that Professor Wang is under investigation by law
enforcement," the letter said.

"While the outcome of those investigations may ultimately bear on Professor Wang's continued appointment at IU, the mere fact of an investigation or of unadjudicated allegations cannot justify failure to comply with university policies on the part of the administration."

"It is fundamental that individuals are presumed innocent until proven guilty," the letter said. "Silence fuels suspicion and distrust and makes shared governance harder."

Matthew Gutwein, a lawyer who had been representing Wang in connection with the university's investigation, did not immediately respond to a request for comment Monday.

An FBI spokeswoman said, "I can confirm the FBI executed federal search warrants at homes in Carmel and Bloomington Friday."

"We have no further comment at this time," the spokeswoman said.

There is no record of any federal criminal case against either Wang or Ma.

Wang had been the associate dean for research at the Luddy School, according to an archived profile page.

That page notes that his work has been funded by multiple federal agencies and that he has been the principal investigator for research projects totaling nearly $23 million.

"Dr. Wang's research focuses on system security and data privacy with a specialization on security and privacy issues in mobile and cloud computing, and privacy issues in dissemination and computation of human genomic data," notes a Luddy School page that was still online as of Monday.

The couple did not immediately reply to a message from CNBC requesting comment.

CNBC has also requested comment from Jackie Bennett Jr., an Indianapolis criminal defense lawyer. Bennett was seen arriving at the Carmel, Indiana, home Friday with a woman believed to be Ma.

FBI agents, assisted by Department of Homeland Security agents, searched the Carmel residence for more than four hours and removed boxes containing unknown items.

Video obtained by WTHR-TV of the FBI search at the Carmel residence also shows an agent snatching a phone from the woman believed to be Ma, as she stood in front of the home.

Bennett, the attorney, is a former federal prosecutor who served in the office of independent counsel Kenneth Starr from 1995 to 1999, when Starr was conducting a criminal investigation of then-President Bill Clinton.

Bennett questioned Clinton during the president's testimony before a grand jury regarding his sexual relationship with White House intern Monica Lewinsky.