The agency says it has become aware of reports of product substitution or tampering in infant formula products.
It says the problem has turned up when someone returns altered products for a refund, and not normally during the manufacturing process.
The CFIA says there have been no illnesses associated with the complaints.
It says anyone using infant formulas should make sure the security seal is intact and has not been altered or the product substituted.
The agency says infant formula that appears to have been altered should not be used.