Raleigh, N.C. — The state Division of Motor Vehicles issued about 27,000 driver's licenses to people with invalid Social Security numbers, according to a state audit released Tuesday.

The Office of the State Auditor has been conducting "strategic reviews" to determine whether invalid Social Security numbers are being provided to state agencies. In previous reviews, several employees at UNC Hospitals, North Carolina Central University and North Carolina State University were found to have invalid Social Security numbers.

State Auditor Les Merritt called the findings in the state DMV audit the most troubling to date.

“A driver’s license is like a master key that can grant broad access by unlocking multiple doors,” Merritt said in a statement. “It is absolutely imperative to spend the resources to get a reliable database going forward and clean up all licenses that have been improperly issued.”

The audit found that out of the 8.1 million Social Security numbers provided to DMV, just under 27,000 were invalid. The number doesn't include the 1.7 million driver’s licenses in the DMV database that don't contain Social Security numbers.

“The hole we discovered was that DMV did not review previously issued licenses. That hole presents a potential threat to homeland security and exacerbates the problem of identity theft,” Merritt said.

The DMV didn't require Social Security numbers to issue a license before last year. Since August, the agency has used an online verification program that allows employees to check the authenticity of Social Security numbers with what officials call "ironclad accuracy."

The invalid numbers were discovered by cross-checking the DMV database with the Social Security Administration’s ranges of validly issued SSNs and its file of deceased individuals.

Almost 12,800 of the invalid numbers belonged to dead people. About 7,500 of the people who provided those numbers had revoked or expired driver's licenses.

About 7,200 of the people providing other invalid Social Security numbers also had revoked or expired licenses, according to the audit.

DMV Commissioner George Tatum said the problem involves fewer than 1 percent of all North Carolina drivers. Although some of the discrepancies might be criminal, others likely involve simple errors or women who failed to register their married names with the Social Security Administration, he said.