(Bloomberg) -- Canadian Imperial Bank of Commerce and Bank of Montreal are alerting clients that “fraudsters” claimed on May 27 to have accessed personal and financial information of some customers.

The accounts of about 40,000 clients may have been electronically breached, CIBC’s online bank, Simplii Financial, said in a statement Monday. Bank of Montreal said separately that fraudsters contacted the Toronto-based lender saying they had certain personal and financial information for “a limited number” of customers.

“We believe they originated the attack from outside the country," Bank of Montreal said in its statement. “We took steps immediately when the incident occurred and we are confident that exposures identified related to customer data have been closed off."

CIBC said there’s “no indication" that clients who bank through the main bank were affected.

To contact the reporter on this story: Doug Alexander in Toronto at dalexander3@bloomberg.net

To contact the editors responsible for this story: Michael J. Moore at mmoore55@bloomberg.net, ;David Scanlan at dscanlan@bloomberg.net, Jacqueline Thorpe

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