There are many unanswered questions in the federal investigation into two physicians at Tenet Healthcare Corp.'s Redding Medical Center, but one fact is already abundantly clear: their names.

The two heart doctors who are at the focus of the probe, Dr. Chae Hyun Moon and Dr. Fidel Realyvasquez, were identified last week in an affidavit by an agent of the Federal Bureau of Investigation. The affidavit was filed as part of the agency's request for a search warrant seeking evidence that would back up allegations that the two performed unneeded surgeries and other invasive procedures.

Health-care and white-collar crime attorneys said that the decision to make the doctors' names public is a relatively unusual one. Federal investigators commonly keep names of their targets under seal in such matters until they are ready to bring formal charges. They do both to protect the reputation of those under investigation and to avoid tipping off the targets and potentially weakening any eventual case.

"It is highly unusual for an affidavit in support of a search warrant to be disclosed ... before any public charge," says Ron Safer, an attorney with Schiff, Hardin & Waite who was formerly chief of the criminal division in the Chicago U.S. attorney's office. For one thing, he says, prosecutors "are, or should be, very cognizant of the damaging potential" that such a disclosure can have on the reputation of those under investigation. It can be a "neutron bomb," he says.

Neither the two doctors nor Tenet have been charged with any offense. News of the 40-agent raid knocked down by 46% over a four-day period the value of shares in Tenet, the nation's second-largest hospital-management company. They have since rebounded after the Santa Barbara, Calif., company held an explanatory call with analysts and appointed an outside auditor to look into the allegations at Redding, a facility that has collected unusually high Medicare program payments for expensive procedures.

It's not clear who made the ultimate decision not to seal the 69-page affidavit. Michael Skeen, the FBI special agent who signed it, declined to comment or discuss the matter and referred questions to the U.S. attorney's office in Sacramento. A spokeswoman for that office declined to comment. Nick Rossi, an FBI spokesman, said he couldn't discuss the specific case, but "there is a presumption that publicly filed documents should be made publicly available and that presumption is strengthened any time public health or public safety is involved."

Malcolm Segal, a Sacramento attorney representing Dr. Realyvasquez, said he was surprised and "uncomfortable" with the decision to unseal the affidavit before he had an opportunity to discuss its contents with prosecutors. "We will be prepared to respond ... when offered an opportunity to do so," he said. "To the extent that there are any allegations of wrongdoing, he categorically denies them."

Dr. Moon's attorney, John W. Reese, released a statement that said his client "categorically denies" the allegations and is "particularly troubled by the government's decision to make public affidavits that are generally sealed until the conclusion of the investigation, and has serious questions about the motivation behind that decision."

The affidavit itself is detailed and vivid: In one case, the affidavit says, a physician interviewed by the FBI claimed that a patient received a "four-vessel bypass surgery" despite "no evidence of any obstructive coronary artery disease." A series of examples make the argument that Drs. Moon and Realyvasquez performed various procedures, including heart catheterization, angioplasty and heart-valve replacement surgery, on relatively healthy patients.

The document doesn't name any of the doctors or other witnesses interviewed by the FBI. In addition, the patients' identities are shielded by law, says Ellen Moskowitz, a health-care attorney at Proskauer Rose LP in New York. "The kind of privacy rights that targets have before they are indicted is something quite different from what patients have," she said. Moreover, doctors who are the focus of a federal probe "get no particular protection by virtue of being physicians."

But the nature of doctors' work, and the importance of reputation, could make such revelations particularly difficult and sensitive. Physicians have mounted a strong political push to increase their protections against civil medical malpractice suits, but the revelation of a potential criminal case, with the weight of the government behind it, may raise the ante even higher. Doctors "take it personally even if their patients never find out about it," says Neil Vidmar, a professor at Duke University's law school who has focused on medical issues. "It has an impact on your life."

Write to Anna Wilde Mathews at anna.mathews@wsj.com ² and Rhonda Rundle at rhonda.rundle@wsj.com

Updated November 6, 2002