Shares of Canopy Growth Corp. (WEED.TO) fell in early trading Tuesday as Canada’s largest medical marijuana company vows to defend itself in a class-action lawsuit related to a recent tainted cannabis scare.

Last year, Mettrum Ltd. – a company now owned by Canopy – and Organigram Inc. were found to be selling marijuana that contained the controversial pesticide myclobutanil – a chemical that can lead to serious health problems. Separate lawsuits have been filed against the companies, with both suits asking the courts to refund patient money and pay additional damages.

Canopy was aware of the extent of the problem when it bought Mettrum and will “vigorously defend itself,” the company said in a statement Tuesday.

“Canopy Growth was, and continues to be satisfied with Health Canada's independent decision to classify the Mettrum recall as a Type III recall, defined as ‘a situation in which the use of, or exposure to, a product is not likely to cause any adverse health consequences,’” the company said.

The tainted marijuana scandal resulted in management changes at both companies. Mettrum CEO Michael Haines left after Canopy completed its takeover in January. Organigram announced that Greg Engel will become the company’s new CEO next week as Denis Arsenault, its CEO at the time of the recall, takes on the role of executive chairman.