Canada's Desjardins credit union announced Thursday that the personal banking information of 2.9 million customers had been stolen by an employee and distributed to outside parties.

The nation's largest credit union and fifth-largest in the world, with Can$304 billion (US$230 billion) in assets under its management, had noted unauthorized access to its members' information last December, but it was only confirmed by police last Friday.

In a statement it said police confirmed to the credit union that the personal information of 2.9 million members "had been shared with individuals outside the organization. This includes 2.7 million individual members and 173,000 business members."

This included names, date of birth, contact information and banking habits. Passwords and other security information were not compromised.

The employee responsible for the breach has since been fired, and Desjardins has put in place additional security measures, Desjardins Group senior vice president Denis Berthiaume told a press conference.

He said the credit union would offer free credit monitoring to affected members, while promising to refund any losses in the event of fraud related to the breach.

Police arrested the suspect but then released him while its investigation continues.

"This major incident affecting Desjardins Group today puts into perspective the omnipresent risk that now weighs on all organizations in terms of information security risks," Quebec's financial sector regulator said in a statement.