An undercover investigator with the U.S. Transportation Safety Administration passed through an airport body scanner repeatedly while carrying a handgun that went undetected, according to an NBC report.

A high-ranking source inside the TSA divulged the information, NBC said, after a covert test of body-scanning security at Dallas-Fort Worth International Airport.

The female undercover agent concealed a pistol in her undergarments and passed through the body scanners several times, and each time the handgun was undetected.

None of the TSA security personnel who failed to spot the handgun in the body scans was disciplined, according to the source cited by NBC.

The TSA acknowledged it frequently conducts covert testing, but does not comment on the results.

"However, advanced imaging technology is an effective tool to detect both metallic and non-metallic items hidden on passengers," it said.

The effectiveness of the scans still relies on people monitoring the screens to pay close attention.