NEW YORK (AP) — A New York City apartment was used to cook crystal meth on a scale usually only seen in non-urban settings, authorities said Wednesday

The Drug Enforcement Administration and local prosecutors announced they had dismantled the illicit lab and seized 22 pounds (10 kilograms) of meth. The supply included about 2 pounds (1 kilogram) that had been converted into the crystalized version that users can smoke, they said.

The lab — located in a six-story residential building in the Bronx across the street from a grade school — was using chemicals that can emit toxic fumes, cause fires and even explode if mishandled, they said.

“It is rare and extremely dangerous to discover a methamphetamine conversion lab in a densely populated area like New York City,” Special Narcotics Prosecutor Bridget Brennan said in a statement.

Ray Donovan, head of the DEA’s New York office, called it further evidence that Mexican drug cartels are getting more aggressive about trafficking meth in a market traditionally dominated by cocaine and heroin.

An investigation was launched after three men were spotting hauling gallon drums of acetone into the vacant apartment. They were arrested on drug possession and other charges.