Global ride-sharing startup Uber said Friday a data breach last year may have allowed a hacker to gain access to the license numbers of some 50,000 of its drivers.

Uber said in a statement it identified "a one-time access of an Uber database by an unauthorized third party" in September 2014.

"Immediately upon discovery we changed the access protocols for the database, removing the possibility of unauthorized access," the statement from data privacy manager Katherine Tassi said.

"We are notifying impacted drivers, but we have not received any reports of actual misuse of information as a result of this incident."

Uber said it also filed a lawsuit to be able to gather information to help identify and prosecute the hacker.

The investigation found the breach "impacted approximately 50,000 drivers across multiple (US) states, which is a small percentage of current and former Uber driver partners," the statement said.

The Los Angeles Times reported that some 20,000 of the Uber drivers impacted were in California.

Uber said it was offering free credit monitoring to those affected to guard against the license information being used for identity theft.

Identity theft is the largest single element in US consumer fraud complaints, according to a Federal Trade Commission report Friday which cited 332,000 cases in 2014.

Uber joins the ranks of other companies hit by data breaches including retailers Target and Home Depot and banking giant JPMorgan Chase, each of which saw millions of customers affected.