Stratford police are warning that a new form of concentrated marijuana known as shatter has been found in the city.

According to police, unusually high levels of tetrahydrocannabinol, or THC, make shatter very toxic and addictive.

"Marijuana could be anywhere between five and eight per cent THC," said Insp. Sam Theocharis. "This is closer to 70 or 80 per cent."

Police seized an amount of the drug, which sells for $100 per gram, on Tuesday during an investigation. Police would not specify how much of the drug they found, except that it was enough to be repackaged and sold in smaller quantities.

Two men in their 40s have been arrested and face numerous charges, including possession for the purposes of trafficking.

Drug causes extreme, long-lasting high

Theocharis said this is the first time that police are aware of shatter showing up in Stratford.

"I would hesitate to say where and when," he said, "but I can guarantee you that if we've seen it in Stratford, other communities in southwestern Ontario have seen it as well."

In fact, Waterloo Regional Police confirmed that shatter had been found in the region in January.

The drug is named shatter for its brittle texture and tendency to break into glass-like shards. It produces an extreme, long-lasting high, said Theocharis, which is what makes it addictive.

"The last thing we want...is to have it show up at any of the local schools and the principals and teachers not know what it is," he said.

According to the Centre for Addiction and Mental Health, about nine per cent of people who use marijuana become dependent on it. In addition, the centre says that the higher the concentration of THC, the greater the risk of mental health problems for drug users.