DENVER — Colorado regulators have issued an US$8.9-million fine against Uber's parent company for allowing employees with serious criminal or motor vehicle offences to work for the company.

The Colorado Public Utilities Commission said Monday that it launched an investigation into the ride-hailing service last year after an Uber driver was accused of assaulting a passenger in Vail.

Within the last year and a half, the commission says it found that nearly 60 Uber drivers were allowed to work in Colorado despite having previous felony convictions, including a former prison escapee, major traffic violations or problems with their driver's licences.

Last week, two women who said they were sexually assaulted by Uber drivers filed federal lawsuits in San Francisco faulting the company's background checks.

Uber didn't immediately respond to a request for comment.