SANTA ANA, Calif. (AP) — Investigators say a series of damaging explosions across OrangeCounty have been attributed to the manufacturing of hash oil, the potent marijuana byproduct.

The Orange County Register reports the Sheriff's bomb squad has been called to investigate more than half a dozen THC-related explosions in the last 18 months.

A recent blast at a condominium complex in Tustin left two men badly hurt.

The county Burn Center says it has treated at least six patients this year who suffered severe injuries while making hash oil.

Tustin Police Lt. Paul Garaven tells the newspaper the do-it-yourself drug is gaining popularity because while marijuana has about 15 percent THC — the main intoxicant in cannabis products — hash oil has a THC rating of 30 to 80 percent.