SACRAMENTO, Calif. (AP) — Researchers and federal authorities are finding powerful and potentially lethal pesticides at nine of every 10 illegal marijuana farms in California this year.

That's a jump from chemicals found at about 75 percent of illegal growing operations discovered on public land last year, and six times as high as in 2012.

Federal and state officials on Tuesday announced the results of a summer-long crackdown prompted in part by new concern over the increase in the use of the highly toxic pesticide carbofuran.

Researcher Mourad Gabriel says the pesticide is so powerful that less than a teaspoon can kill a 300-pound bear.

The crackdown aided by $2.5 million in federal money led to more than 95 investigations and the removal of more than 10 tons of fertilizer, pesticides and chemicals.