Canadians are still left without answers as to how a man was able to take 22 vials of biological material from Canada's National Microbiology Laboratory in Winnipeg and cross the Manitoba-North Dakota border.

"We don't do body searches on people leaving the building that's not necessary," Dr. David Butler Jones, Canada's chief public health officer, told CTV Winnipeg.

American border guards stopped Konan Michael Yao, a former employee of the laboratory, in Pembina, N.D. on May 5. When they opened his truck, the guards discovered 22 vials of biological material wrapped in aluminum foil in a plastic bag.

Nobody on either side of the border has revealed what the vials contained, but U.S. authorities say the material was not infectious.

The American Centre for Disease Control is testing the substances to determine what they are while Yao remains in custody in an undisclosed area, say U.S. authorities.

American court documents allege Yao told officers he was heading to the Bio-Defence Research Laboratory in Bethesda, Md. for a new job.

Yao told U.S. border guards he took the vials on his last day at the lab in January. Since he was working on a vaccine for the Ebola virus and HIV, he said, he took the material with him because he didn't want to lose his research.

The Public Health Agency of Canada did not name Yao, but said the man in custody stopped working at National Microbiology Lab in January.

The Canadian agency said he only worked with non-infectious material and never had access to the HIV or Ebola virus.

The most infectious pathogens can't be handled without body suits and respirators, so scientists say it would be too hard to sneak them out, the agency added.

"You're only allowed to work with materials that you're allowed to work with, in other words people do not have general access to the lab, so if you're not working with infectious material, you have no access to infectious materials," said Butler Jones.

Health Canada is looking into the matter.

With a report from CTV Winnipeg