Roughly a million dollars worth of tainted medical cannabis has been destroyed and concern is mounting that Health Canada has no way of knowing how big the problem actually is, the Globe & Mail reports.

Canopy Growth Corp., which recently acquired Mettrum Ltd., said this week that it has written off about $800,000 of costs owing to a series of product recalls Mettrum announced beginning last November.

The recalls came after Mettrum was caught using a banned pesticide in products that were sold in 2016. A former Mettrum staffer said that he saw employees spraying plants with myclobutanil as far back as 2014, despite knowing the chemical is prohibited, and that staff hid the pesticide in the ceiling tiles of the company’s offices when Health Canada inspectors visited the site.

Read the full story by reporter Grant Robertson here.