A senior researcher at the Saskatoon Cancer Centre at the University of Saskatchewan is under investigation for running unauthorized experiments — injecting mice with listeria bacteria.

CBC News has learned Dr. Jim Xiang injected lab mice with the bacteria in three separate experiments in July, November and December, although he had no biosafety permit to work with listeria. He also failed to get permission from the university's animal ethics committee, the university has confirmed.

A worker in the laboratory discovered and reported the unauthorized work on Jan. 4, said Jim Basinger, the university's vice-president of research.

"The experiments were shut down, essentially immediately, and the investigation initiated and the public health protected," Basinger said.

'From what we're able to determine, it really looks like there should have been a negligible risk to the public or any patients or staff.'—Infectious disease specialist Stephen Sanche

The university's animal ethics and biosafety committees are investigating. Any repercussions for Xiang will depend on what these committees recommend.

Investigators are trying to make sure no cancer patients were exposed to the infectious bacteria.

Listeria can be deadly to the young, the old, and people who have weakened immune systems.

"I can understand why people would be concerned about bacteria being propagated in a building that is being used for patient care," said Stephen Sanche, an infectious disease specialist at the university. "From what we're able to determine, it really looks like there should have been a negligible risk to the public or any patients or staff."

CBC spoke with Xiang, who said what happened was an oversight in which the proper paperwork was not filled out.