MURFREESBORO, Tenn. -- The growing scandal over contamination and colonoscopies at the Veterans Affairs has been reported for six months now. Tuesday, Congress will convene hearings to determine just what went wrong.

The Channel Four I-Team zeroes in on a possible theory: Could a big company that makes medical cleaning devices have encouraged VA hospitals to use a faster shortcut?

An expert said that shortcut may have morphed into a dangerous situation that put health potentially at risk for years.

A health care worker spotted something wrong in December after a colonoscopy. Within weeks, thousands of veterans were worried about their health. Nearly 30 patients so far in Tennessee have hepatitis, even HIV, and it all comes down to a little green valve on the flushing end of a colonoscopy machine.

"The connector used is similar to the appearance to the proper valve," said a VA doctor at a press conference.

An improper valve ended up on a key piece of tubing, and it seems no one noticed or knows why.

What they should have seen is two green wings, which means fluid correctly flows just one way. But a single, green wing on that piece of tubing means there's potential that bacteria from one patient could spread to the next.

"What are they finding?" asked lawyer Mike Sheppard. "What's the cause?"

The VA said it has no idea, apart from "unclear product instructions," how that wrong two-way valve got into the mix and why it stayed that way perhaps for years.

The I-Team has one possible explanation, and it has to do with a quicker way of cleaning.

In April 2001, a company called MediVators put out a bulletin saying it had come up with a way to use its quicker machine to clean internal parts of a colonoscope, instead of spending so much time doing it by hand.

Though the instruction manual recommends a certain tube be used to manually process the channel, MediVators said to use a different method to connect to the machine for "superior flow."

The memo also said to make the customers aware of these recommendations and the "necessary hookups."

So did the necessary hookups involve the incorrect two-way valve? One expert suspects it did.

"It is virtually impossible -- my tests indicate completely impossible -- to reprocess that ... tubing with the correct valve in place," said Lawrence Muscarella, an expert in colonoscope design and infection control.

"It would appear that hospitals may have been instructed to do this, if innocently," said Muscarella. "This is potentially the cause of this problem, because to reprocess this irrigation tubing automatically instead of manually, you have to remove the correct valve and put an improper valve that, while it facilitates reprocessing of the tubing, can result in patient contamination of the irrigation pump."

Contamination is precisely what happened in Murfreesboro. The VA there did use a machine to clean parts of its colonoscopes, as did the VA in Miami. In both cases, the machine used was MediVators.

But the CEO of MediVators said the theory is all wrong. He said the bulletin came about because a customer requested a way to clean the tube and scope all at once, and the company complied.

"We do not want to have any customer just dream up, on their own, a method to reprocess the scope or component," said CEO Roy Malkin.

Malkin also sent a picture as proof the rigging works. There's the tube in question, connected with the correct two-winged valve. The I-Team could not find this photo duplicated in any of the directions for using a MediVators machine.

If this theory is true, does it suggest a much bigger problem? If this were a worldwide recommendation for eight years, how many other hospitals may have switched that valve? How many patients could face the consequences?

"You can imagine the concern and fear and anxiety in these veteran families not knowing what the next step is," said Sheppard.

In the six months the issues have been reported, it does not appear from the Food and Drug Administration database that any of the companies involved has filed a medical device report -- something required whenever there's a problem with a medical device.

And while the MediVators machine is approved by the FDA for cleaning colonoscopes, it's unclear if the newer instructions for cleaning that tube were ever specifically approved.

MediVators insists that it has complied with all rules and regulations on safety instructions.