Denver city officials have put a hold on 60,000 plants after concerns were raised that they may be contaminated with unapproved and possibly harmful pesticides. 11 other grow sites have hand plants put on hold through the same initiative. At least one of the cultivators has already destroyed over 1,000 of its own plants.
There is no standardized testing of marijuana in Colorado, but according to a USA Today report on the quarantine, the city of Denver has begun the beta testing of plants with the hope of expanding the testing in the near future. There is some concern that the rash of quarantines could lead to a shortage in the Denver area.