MONTREAL -- The packages of mysterious seeds that have been making unsolicited appearances in mailboxes across North America are drawing attention to an online review scam that has recently appeared in Canada.

The Canadian Food Inspection Agency warned gardeners last week not to plant any seeds they received in the mail without ordering, warning that they could be from invasive species or even carry pests.

While Canadian authorities have not provided an update, the United States Department of Agriculture has suggested the seeds may be part of a "brushing" scam, where sellers send unsolicited items to random customers and then post fake positive reviews online.

Jessie St-Cyr, a spokeswoman with the Better Business Bureau, says this type of scam has recently begun popping up in Canada.

She says sellers send light or inexpensive items to people so they appear to be verified customers when reviews are posted online in their names.

While customers usually aren't charged for the items, she said recipients should change their passwords for online retail sites and verify bank statements to ensure fraudsters aren't accessing sensitive information, such as credit card numbers.