Marijuana seized from a ring of illegal grow houses in rural Maine is laden with dangerously high amounts of mold, toxic fertilizers and banned insecticides, newly released chemical testing results confirm.

All 21 cannabis samples taken from illegal grow houses in early 2024 and submitted for testing by the Office of Cannabis Policy were tainted with levels of heavy metals, chemicals or mold. Only three samples would have passed the state’s recreational cannabis testing regimen.

The results were obtained through a media request with the agency.

Many of the chemicals detected in the tests are acutely toxic or environmentally hazardous, said Nick Chamberlain, spokesperson for the Portland company Nova Labs, which conducts testing but did not handle these samples.

“Some of these are irritants, some of these are fatal if swallowed or inhaled,” Chamberlain said. “They could all theoretically be fatal at certain levels … There are a couple of results in there that are pretty shocking.”

Several samples maxed out the readings for mold spores in cannabis. Many of the homes used for illegal growing operations have large black mold infestations, police have said after raids.

While cannabis testing cannot differentiate between benign or harmful spores, Chamberlain said it is extremely unlikely that cannabis with such high readings would be safe to consume.

Many tests contained the fungicide Eagle 20EW, which creates cyanide gas when ignited and inhaled (i.e. smoked). Others had the banned insecticide DDVP, which the Environmental Protection Agency said is often smuggled in from overseas.

Other black market fumigants banned in the U.S. and imported from China are often found inside the grow houses, police say, though it remains unclear what exactly those chemicals are. Laboratories often do not test for them because they are illegal.

The cannabis plant is a bioaccumulator, meaning it absorbs and retains all the chemicals, toxins and contaminants in its water, air and soil, Chamberlain said. Some toxins can also present different hazards when they interact with other chemicals, are set aflame like a joint or swallowed like an edible, he said.

“It’s not only the chemical itself, it’s the stuff that happens when you vaporize or heat up that chemical as well,” Chamberlain said. “A lot of pesticides end up breaking down into things that are even more dangerous than the original pesticides.”

Police have linked dozens of illegal growing operations to Chinese organized crime groups, but many have transitioned to Maine’s medical marijuana market, which has no testing mandates.

Industry groups have previously advocated for illegal grow houses to transition into the medical market, saying they would teach them best practices to grow safely. But many samples of illegal cannabis contained the same chemicals as licensed “grow house” operations.

The operations often coordinate with one another to share growing techniques, workers and materials like fertilizers and soil, police and those involved with the operations have said.

“It’s cookie cutter, from how they build the growing operations, what chemicals they use,” said Somerset County Sheriff Dale Lancaster, whose office has raided more than 20 illegal growing operations. “It’s replicated from place to place.”