Canada’s privacy commissioner has launched an investigation into the massive Capital One data breach that exposed personal data of roughly six million Canadians, including about one million social insurance numbers.

The Office of the Privacy Commissioner of Canada announced Wednesday that it has opened its own investigation into the matter after being in touch with the company. 

As the investigation unfolds, Canadians should not give out any sensitive information over the phone to anyone who claims they’re calling from Capital One. The Office of the Privacy Commissioner said it was alerted that the company will not be calling customers over the phone regarding the incident.

“Should individuals receive calls claiming to be from Capital One regarding this incident, they should not provide any information and instead should call the number listed on the back of their credit card,” the office said.

Anyone who notices suspicious activity on their Capital One account is advised to report it to police, contact the Canadian Anti-Fraud Centre and inform Service Canada. Capital One says it will contact affected customers about a free credit monitoring and identity protection services.

No credit card numbers were compromised in the breach, the company said. Still, customers could consider asking for a new card and number, or close their account.

An estimated 100 million American clients were also affected by the breach. Phone numbers, email addresses, dates of birth, credit scores and self-reported income were among the information that the hacker was able to access.