Bank of Montreal and Simplii Financial, Canadian Imperial Bank of Commerce’s direct banking unit, are both warning their respective clients that personal and account information may have been compromised.

Simplii said early Monday morning in a release that approximately 40,000 of its clients may have had data accessed by fraudsters, and that it is contacting clients and enhancing its online fraud monitoring and security measures.

The company issued the warning after it learned Sunday that fraudsters may have electronically accessed certain data for thousands of its clients.

Following Simplii’s warning, BMO (BMO.TO) also said it was contacted Sunday by fraudsters, adding that the bank believes the attack originated from outside Canada.

BMO said less than 50,000 clients have been affected. 

“We took steps immediately when the incident occurred and we are confident that exposures identified related to customer data have been closed off,” BMO said in a statement. “We have notified and are working with relevant authorities as we continue to assess the situation.” 

Simplii said there is currently no indication that CIBC (CM.TO) clients have been affected.

"We're taking this claim seriously and have taken action to further enhance our monitoring and security procedures," said Michael Martin, senior vice-president of Simplii, in a release.

In an interview with BNN Bloomberg Monday, former Ontario privacy commissioner Ann Cavoukian called the breaches “truly unacceptable.”

“It should be shocking, because you expect your finances – among the most sensitive personal information that exists – to be very, very strongly protected,” Cavoukian said.

“The question I would ask is … They’re saying they’re now going to implement enhanced security measures to protect your financial data. Well, why the heck didn’t they employ enhanced measures to begin with?”

Simplii advised customers to use a complex password and pin, and to monitor accounts for unusual activity.

The company also said fraud victims will receive 100 per cent of any money lost from the affected bank account.

CIBC launched Simplii as a new brand in November after announcing it was winding down its relationship with Loblaw’s President’s Choice Bank and transferring PC Financial clients to Simplii in the process.

Simplii offers no-fee banking to its customers through online, phone and mobile channels.

Federal Finance Minister Bill Morneau has spoken to the CEOs of the affected institutions, and the finance ministry is “monitoring the situation closely with the Office of the Superintendent of Financial Institutions,” spokesperson Jocelyn Sweet said in an emailed statement.

"Cyber security and the protection of personal and financial information is a priority for the government," Sweet said.

A Bank of Nova Scotia spokesperson said in an email the bank has nothing to report at this time, while a Royal Bank of Canada spokesman said there is no indication that its bank has been affected. 

Toronto-Dominion Bank also said there's no indication that its customers have been affected.