MILWAUKEE – More than 22,000 veterans who underwent prostate biopsies at veterans’ hospitals across the country are being warned that improperly sterilized equipment may have exposed them to deadly viruses.

Officials said Friday it was unlikely someone could get infected by the equipment, and no patient is known to have been sickened.

Still, the U.S. Department of Veterans Affairs decided to offer free blood tests as a precaution after officials in Maine questioned whether the cleaning procedure was thorough enough, said VA spokesman Jim Benson.

The prostate biopsy equipment includes a probe that, if improperly cleaned, could retain traces of body fluids containing the viruses that cause hepatitis or AIDS.

Since April, the VA has alerted patients of potential inadequacies with the biopsy cleaning procedure at 21 medical centers in 18 states, plus Puerto Rico.

So far, about 7,000 vets contacted the VA after receiving the letter and about 2,000 have been tested, Benson said.

“It’s too soon to have any information on their test results because each of the potential diseases we might be worried about require not only initial tests but confirmatory tests as well,” Benson said. “Right now our first priority is getting information out to every veteran.”

Dennis Maki, an infectious disease expert at the University of Wisconsin-Madison, said the prostate examination technique involves inserting a stainless steel scope about the diameter of a pencil into the rectum. Then doctors use a hollow needle to draw a sample from the prostate gland.

The standard sterilizing procedure called for the equipment to be flushed with a disinfecting solution, but officials grew concerned that blood and fecal residue might remain unless the tube were physically scrubbed as well.

It’s possible but unlikely that someone could get infected that way, said Michael Erdmann, chief of staff of the Milwaukee VA Medical Center.

“We’re concerned for the safety of our patients, but really, the odds are really quite low,” he said.

The problem wasn’t manpower so much as cleaning instructions provided by the manufacturer that didn’t specify the need for a brush, Erdmann said.

The equipment was made by B-K Medical Systems in Denmark. Company officials from neither B-K nor its Massachusetts-based parent company, Analogic, immediately returned phone calls by The Associated Press on Friday.

Michael O’Rourke, a spokesman for the Veterans of Foreign Wars, said he was satisfied with the VA’s response. “I don’t know what more they can do,” he said.

Peter Gaytan, the director of veterans affairs for the American Legion, said his group is reaching out to veterans to make sure the VA has addressed their concerns.

“What the American Legion wants to make sure is that this mistake isn’t the responsibility of overworked VA staff, and if it is, they need to hire more people,” he said.