As the legal cannabis industry booms in Colorado, residential cultivators around the state are leaving behind large amounts of mold and extensive property damage.

Denver detective Brian Matos estimates one in ten homes in the city grow cannabis – ““everywhere from one plant to 1,000 plants.”

A 2010 study showed it would require nearly 50 plants to produce mold spores which would cause the highest level of property damage. Colorado currently allows adult residents to cultivate up to six plants at home.

When David and Christine Lyn of Douglas County had recently purchased their Colorado home for $368,000, they discovered the old occupants had purposely diverted an electrical line from the property to conserve on the cost of power required to run a growing operation.

After they handled the power line issue, the new owners found thousands of square feet of mold beneath flooring, basement drywall, and ceilings. The pattern of mold reached from floor to ceiling and indicated the source didn’t come from outside.

Law enforcement authorities stated they saw more property damage appear from cannabis growing operations, the Lyn property being one of the worst cases witnessed.

Gangs in Colorado primarily grow the product in commercial warehouses, middle class properties, and high-income neighborhoods according to the federal Drug Enforcement Agency.

“We see mold issues, fire hazards. You need more power, so they try to set up their own electrical systems,” said Matos.“Breakers are popping, transformers are blowing out, power cords are sitting in standing water. They try to do this in their basement. How many people try to grow tomatoes in their basement,” he added.

Mold is the biggest environmental danger caused by the amount of humidity injected into the home from cannabis plants, which can seriously affect people with asthma and other respiratory conditions.

Colorado requires sellers to disclose if a home has been contaminated by illegal substances, with the state reminding brokers in 2015 that cannabis contamination must be disclosed even if it was legally grown in the home.