A security breach at car service Uber may have disclosed the names and driver's licence numbers of about 50,000 drivers across multiple states, the company said in a statement on Friday.
The data breach involved current and former Uber drivers, and the company has notified attorneys general in states where those drivers live, including California.
"To date, we have not received any reports of actual misuse of any information as a result of this incident," the company said. However, Uber advised drivers to monitor their credit reports for fraudulent transactions.
The company has raised more than $4 billion from prominent venture capital firms such as Benchmark and Google Ventures, valuing Uber at $40 billion and making it the most valuable startup in the United States.
Uber also filed a lawsuit in a federal court in San Francisco on Friday against the unnamed individual who accessed the company's files. Such litigation can be used to help uncover who committed the breach.
Uber said the breach occurred in May 2014 and was discovered in September. The company said it changed database access protocols and began an investigation.