OTTAWA – Canada's privacy commissioner has opened a formal investigation into the Uber hack that saw millions of customers' personal information stolen.

Uber admitted to the 2016 hack on Nov. 21. Uber CEO Dara Khosrowshahi said that "two individuals outside the company had inappropriately accessed user data stored on a third-party cloud-based service," used by the ride sharing app.

The hackers were able to access 57 million Uber users' personal information including names, email addresses and cell phone numbers.

Though Uber has been unable to confirm how many Canadian customers were affected by the hack, Privacy Commissioner Daniel Therrien is looking into it, his office confirmed Monday.

"We have now opened a formal investigation," said privacy commissioner spokesperson Tobi Cohen in an email to CTV News.

Citing confidentiality, Cohen said no further details are available about the probe.

A spokesperson for Uber Canada told CTV News that Uber will continue to work with the privacy commissioner as the investigation goes forward.

"The privacy of riders and drivers is of paramount importance at Uber," said Jean-Christophe de le Rue in an email.