A Massachusetts laboratory says it’s found vitamin E acetate in marijuana vape cartridges tested across Massachusetts, but not in vapes sold at licensed cannabis businesses.

MCR Labs had developed a way to test for the chemical, which is an oil additive found in THC-based vape products that the U.S. Centers for Disease Control and Prevention says is now a “very strong culprit” in the ongoing national outbreak of illness that has sickened thousands and caused three deaths in Massachusetts.

The lab began screening products on Sept. 20, taking 109 samples from marijuana vape cartridges submitted by consumers and manufacturers.

Of those samples, nine resulted in a positive finding for vitamin E acetate. In a statement from the lab, researchers noted that some of those samples contained “more than 50 percent” of the additive by weight.

But they note that none of the samples were submitted by businesses “licensed to produce or manufacture cannabis products” in Massachusetts.

“Every vaping product supplied to us by a regulated producer has been shown to be free of this particular additive,” they wrote.

The CDC said last week it had found vitamin E acetate in the lung fluids of 29 patients with vaping-related lung injuries. Medical authorities had long suspected that the additive has played a role in the outbreak of disease.

On Tuesday, the Massachusetts Cannabis Control Commission moved to quarantine all marijuana vape products except cannabis flower vaporizers, which will only be available for medical marijuana cardholders.