CHATTANOOGA, Tenn. - A congressional panel is pressing the Department of Veterans Affairs to disclose tomorrow whether nonsterile equipment that may have exposed 10,000 veterans to HIV and other infections was isolated to three Southeast hospitals or part of a wider problem.

"Somebody is going to have to take responsibility," said U.S. Rep. Phil Roe of Tennessee, the ranking Republican on the House Committee on Veterans Affairs oversight and investigation subcommittee.

The subcommittee scheduled tomorrow's hearing in Washington to discuss mistakes involving endoscopic equipment used for colonoscopies and other procedures at its hospitals in Miami; Murfreesboro, Tenn.; and Augusta, Ga.; with top agency officials and to receive a yet-unreleased report by the VA's inspector general.

Roe said he had not yet seen the report but was told in a briefing that the inspector general conducted a random check at 42 facilities.

VA officials have said that problems discovered at more than a dozen other sites did not warrant follow-up blood tests. Roe, a private physician, questions whether the problems were isolated to the three hospitals.

"I think this was an institutional breakdown," Roe said.

Since February, the VA has been warning about 10,000 former patients, some of whom had colonoscopies as long ago as 2003, to get blood tests for HIV and hepatitis.

The VA's chief patient-safety officer, Jim Bagian, has said no one will ever know whether the patients with HIV and hepatitis were infected because of improperly operated or cleaned equipment used in colonoscopies at Murfreesboro and Miami, and to treat patients at the VA's ear, nose, and throat clinic in Augusta.

As of Friday, the VA reported that six veterans who got follow-up blood checks tested positive for HIV, 34 for hepatitis C, and 13 for hepatitis B.

VA spokeswoman Katie Roberts did not respond to repeated requests for comment Thursday and Friday.

The initial discovery of an equipment mistake at Murfreesboro led to a nationwide safety step-up by the VA at its 153 medical centers. Since then, the VA says the problems have been discussed with staff at all VA hospitals and with representatives of the equipment manufacturer, Olympus American.

Roe said he believed the VA had been open and trying to keep former patients and the public informed since discovering the mistakes in December. "These people did not intentionally do anything wrong," he said.

A spokesman for the American Society for Gastrointestinal Endoscopy, David A. Greenwald, said in a phone interview that although the VA patients recently tested positive, they could have had the viruses for years, and before the VA treated them, without symptoms.

He said the positive tests for HIV and hepatitis C reported by the VA were far below the frequency of positive tests reported from studies of other groups of veterans. He said the same was likely true of the hepatitis B cases.