To date, about 2,000 of the so-called radio frequency identification, or RFID, devices have been implanted in humans worldwide, according to VeriChip Corp. The company, which sees a target market of 45 million Americans for its medical monitoring chips, insists the devices are safe, as does its parent company, Applied Digital Solutions, of Delray Beach, Fla.

“We stand by our implantable products which have been approved by the FDA and/or other U.S. regulatory authorities,” Scott Silverman, VeriChip Corp. chairman and chief executive officer, said in a written response to AP questions.

The company was “not aware of any studies that have resulted in malignant tumors in laboratory rats, mice and certainly not dogs or cats,” but he added that millions of domestic pets have been implanted with microchips, without reports of significant problems.

The FDA also stands by its approval of the technology.