When the U.S. Food and Drug Administration approved implanting microchips in humans, the manufacturer said it would save lives, letting doctors scan the tiny transponders to access patients' medical records almost instantly. The FDA found "reasonable assurance" the device was safe, and a sub-agency even called it one of 2005's top "innovative technologies."

But neither the company nor the regulators publicly mentioned this: A series of veterinary and toxicology studies, dating to the mid-1990s, stated that chip implants had "induced" malignant tumors in some lab mice and rats.

"The transponders were the cause of the tumors," said Keith Johnson, a retired toxicologic pathologist, explaining in a phone interview the findings of a 1996 study he led at the Dow Chemical Co. in Midland, Mich.

Leading cancer specialists reviewed the research for The Associated Press and, while cautioning that animal test results do not necessarily apply to humans, said the findings troubled them. Some said they would not allow family members to receive implants, and all urged further research before the glass-encased transponders are widely implanted in people.

The FDA also stands by its approval of the technology.

Did the agency know of the tumor findings before approving the chip implants? The FDA declined repeated AP requests to specify what studies it reviewed.

The FDA is overseen by the Department of Health and Human Services, which, at the time of VeriChip's approval, was headed by Tommy Thompson. Two weeks after the device's approval took effect on Jan. 10, 2005, Thompson left his Cabinet post, and within five months was a board member of VeriChip Corp. and Applied Digital Solutions. He was compensated in cash and stock options.

Thompson, until recently a candidate for the 2008 Republican presidential nomination, says he had no personal relationship with the company as the VeriChip was being evaluated, nor did he play any role in FDA's approval process of the RFID tag.

"I didn't even know VeriChip before I stepped down from the Department of Health and Human Services," he said in a telephone interview.

Also making no mention of the findings on animal tumors was a June report by the ethics committee of the American Medical Association, which touted the benefits of implantable RFID devices.

Had committee members reviewed the literature on cancer in chipped animals?

No, said Dr. Steven Stack, an AMA board member with knowledge of the committee's review.

Was the AMA aware of the studies?

No, he said.

___