Washington (CNN) -- The Transportation Security Administration on Friday ordered re-testing of all radiation-emitting full-body scanners after an internal review showed calculation errors, missing data and other discrepancies on paperwork by contractors who routinely check the machines' radiation levels.

As recently as Wednesday, the agency vouched for the safety of the machines, with Homeland Security Secretary Janet Napolitano telling a Senate committee that independent studies concluded the machines are "more than safe."

"The amount of radiation is approximately (the same as that received) as two minutes in the air," Napolitano said.

The TSA reiterated that position Friday, characterizing problems as "record-keeping errors."

But Sen. Susan Collins, R-Maine, said the TSA found problems with more than one-quarter of the reports it reviewed, "including gross errors about radiation emissions."

"That is completely unacceptable when it comes to monitoring radiation," Collins said. "If TSA contractors reporting on the radiation levels have done such a poor job, how can airline passengers and crew have confidence in the data used by the TSA to reassure the public?"

The TSA said all "backscatter" full body scanners will be re-tested by the end of March, the TSA said. It will also require contractors to re-train machine testers, while increasing TSA oversight over the tests.

Further, the TSA said it would ask the National Institute for Occupational Safety and Health (NIOSH) to update its 2008 report.

The announcements came as the TSA, responding to public pressure, posted raw data about radiation tests on its website. The agency also promised to post all future radiation checks on the web site for public review.

The TSA said its internal review looked at randomly selected reports generated over the last two years at 15 airports. The tests are conducted by manufacturers and contractors.

"These reports confirm that each piece of technology reviewed meets all national safety standards," the TSA said. But, the TSA said, the reports contained "inaccuracies." Those inaccuracies included "calculation errors not impacting safety," no reading of background radiation levels, and missing "non-measurement related information."

TSA spokesman Nicholas Kimball said Friday that numerous independent tests have confirmed that body scanners are safe, "but these record-keeping errors are not acceptable."

"We're taking a number of steps to ensure the mistakes aren't repeated and the public will be able to see for themselves by reviewing all future reports online," Kimball said.

Marc Rotenberg, president of a privacy rights group and a critic of the full-body scanners, said the latest development is "more evidence" that the TSA should suspend use of the machines.

A House government oversight subcommittee will hold a hearing on TSA oversight of the full-body scanners on Wednesday.