Personal banking information of tens of thousands of Facebook employees in the U.S. was compromised last month, when a thief stole a number of the company's hard drives from an employee's car.

Hard disk drives - which were not encrypted - include payroll data such as employee names, bank account numbers and four employee social security numbers, according to a Facebook email shared with employees Friday morning.

The drives also included compensation information, including salaries, bonus amounts and some share details.

In total, the drives contained personal data of about 29 US employees who worked on Facebook in 2018, a company spokeswoman confirmed.

Facebook has faced several instances in recent years of disclosing personal data to social network users. However, the stolen drives did not include user data for Facebook, the spokeswoman said.

"We worked with law enforcement during their investigation into a car break-in and theft of a staff bag containing company equipment, while storing employee payroll information on it ... We have not seen any evidence of abuse, and we think this is a burglary," she said in a joint statement with Bloomberg. The takeover instead of an attempt to steal employee information. "

It is noteworthy that the accident occurred on November 17, and Facebook realized that hard drives were missing on the 20th of the same month, according to internal e-mail.