The State Department said Friday it has warned nearly 400 passport applicants of a security breach in its records system that may have left them open to identity theft.

The department has so far notified 383 people — most of them in the Washington, D.C. area — that their passport applications containing personal information, including Social Security numbers, may have been illegally accessed and used to open fraudulent credit card accounts, spokesman Sean McCormack said.

More may be notified as an investigation continues, he said, adding that most of those contacted had not been victimized by identity thieves but all have been offered free credit monitoring for a year.

The breach came to light in March around the same time the department was grappling with cases of workers improperly snooping in the passport application files of presidential candidates, celebrities and athletes, McCormack said. However, he said the cases are not related.

The department notified the 383 passport applicants of their potential vulnerability in August and earlier this month while working with Washington police investigating a credit card and identity theft ring, he said.

The ring was exposed after the March arrest of a man found with 19 credit cards in different names and eight completed passport applications. The names of four of those applicants matched those on four of the credit cards, according to documents filed in the U.S. District Court for the District of Columbia.

McCormack declined to comment on how the man, who has since died, obtained the applications, but he said one State Department employee had been fired as a result.

Following the passport snooping incidents, the department stepped up security for its passport records management, restricting the number of people with access and stepping up mandatory audits and monitoring of the files.