The two laboratories that have been licensed to test non-medical marijuana have been cleared to begin testing, putting in place another crucial link in the supply chain as the Cannabis Control Commission waits to give retail stores the go-ahead to begin sales.

MCR Labs LLC of Framingham and CDX Analytics LLC of Salem received notices to commence operations from the CCC last Wednesday, clearing them to begin testing recreational marijuana in three days. All marijuana sold in Massachusetts must first be tested and approved by an independent lab, so retail sales cannot begin until the testing labs are operational.

“When Massachusetts voters legalized adult-use cannabis, they communicated a desire to purchase products that are safely regulated and properly tested,” CCC Executive Director Shawn Collins said. “The Commission has done scrupulous due diligence to make that vision a reality and ensure licensed independent testing labs maximize public health and public safety.”

The CCC said the “minimum of three calendar days” that the labs must wait until actually commencing operations is to make sure the labs have a chance “to coordinate opening day logistics with their host community, local law enforcement, marijuana establishment colleagues, and other essential stakeholders before adult-use operations begin.”

Both labs already test marijuana for the Department of Public Health’s medical marijuana program and the CCC said that any marijuana the two labs have already tested for the medical marketplace will not need to be tested a second time if it is transferred to the recreational market. That also means that the labs can continue to test medical marijuana during the three-day waiting period and that those products can then be transferred to the recreational marketplace.

Two years ago Thursday, about 1.8 million Massachusetts residents voted to legalize marijuana for adult use. It has been legal since December 2016 for adults 21 and older to use, grow and possess marijuana. The CCC and lawmakers had hoped to launch retail marijuana sales by July 1 but did not meet that goal.