MURFREESBORO, Tenn. -- A lawsuit could be coming at the Veterans Administration for what might be thousands of risky colonoscopies performed at the York Hospital in Murfreesboro.

The Channel 4 I-Team has learned of at least a half-dozen patients who had the procedure there and have tested positive for hepatitis. Yet, the VA is on record saying there are no positive results.

It's been almost three months since the problem was discovered: an incorrect valve on a colonoscopy machine that posed the potential for bacteria to flow out of one patient and into the next.

"We know there were two patients potentially exposed," said Dr. Walter Smalley, of York's gastroenterology division.

But since then, two patients have grown to more than 6,000. In fact, every veteran who had a colonoscopy over the past five years, doctors said, could have been exposed to hepatitis B or C or even HIV.

Wednesday, a Nashville law firm began running an Internet ad, looking for vets who have had the procedure and are worried. The lawyers don't know how many patients they may find. But in documents obtained by Channel 4 News, it is clear that VA doctors are worried about breaking the news to patients.

Last month, one physician wrote to others, "Already I have received positive results for Hepatitis B and C and do not wish to convey this to the patients over the phone, and I am not doing it."

A second doctor wrote, "I also have three critical ... results that are positive already."

Yet another health professional said, "Some of my patients are coming in and getting positives for Hep. C. ... One in particular was neg (sic) in 2007."

But the VA, which has refused to grant an interview on the matter, paints a different picture, saying, "As of Feb. 25, 2009, there have been no positive results reported for any of the patients that have been tested."

Doctors said the difficult part of this puzzle will be to determine whether patients who do turn up with hepatitis might have had it all along.

Regardless, attorneys said, there has been medical damage done.

"We need to get that information from the VA, and we need to probably subpoena that information," said Mike Sheppard.

No lawsuit has been filed yet; the firm is simply wanting to talk with vets who are concerned.