Washington --

A wide-ranging surveillance operation by the Food and Drug Administration against a group of its own scientists utilized an enemies list of sorts as it secretly captured thousands of e-mails that the disgruntled scientists sent privately to members of Congress, lawyers, labor officials, journalists and even President Obama, previously undisclosed records show.

What began as a narrow investigation into the possible leaking of confidential agency information by five scientists quickly grew in mid-2010 into a much broader campaign to counter outside critics of the agency's medical review process, according to the cache of more than 80,000 pages of computer documents generated by the surveillance effort.

Moving to quell what one memo called the "collaboration" of the FDA's opponents, the surveillance operation identified 21 agency employees, congressional officials, outside medical researchers and journalists thought to be working together to put out negative and "defamatory" information about the agency.

FDA officials defended the surveillance operation, saying the computer monitoring was limited to the five scientists suspected of leaking confidential information about the safety and design of medical devices.

While they acknowledged that the surveillance tracked the communications that the scientists had with congressional officials, journalists and others, they said it was never intended to impede those communications, but only to determine whether information was being improperly shared.

The agency, using so-called spy software designed to help employers monitor workers, captured screen images from the government laptops of the five scientists as they were being used at work or at home.

The extraordinary surveillance effort grew out of a bitter, years-long dispute between the scientists and their bosses at the FDA over the scientists' claims that faulty review procedures at the agency had led to the approval of medical imaging devices for mammograms and colonoscopies that exposed patients to dangerous levels of radiation.

Last year, the scientists found that a few dozen of their e-mails had been intercepted by the agency. They filed a lawsuit in September, after four of the scientists had been let go, and the Washington Post disclosed the monitoring in January. But the scope of the surveillance, its range of targets across Washington, and the huge volume of information that it generated were not previously known.

FDA officials said that in monitoring the communication of the five scientists, their e-mails "were collected without regard to the identity of the individuals with whom the user may have been corresponding." The FDA said that those outside the agency were never targets of the surveillance operation but were suspected of receiving confidential information.

While federal agencies have broad discretion to monitor their employees' computer use, the FDA program may have crossed legal lines by grabbing and analyzing confidential information that is specifically protected under the law, including attorney-client communications, whistle-blower complaints to Congress, and workplace grievances filed with the government.

Members of Congress were irate to learn that correspondence between the scientists and their own staffers had been gathered and analyzed.

"It is absolutely unacceptable for the FDA to be spying on employees who reach out to members of Congress to expose abuses or wrongdoing in government agencies," said Rep. Chris Van Hollen, D-Md., who has examined the agency's medical review procedures.