ST. LOUIS – Mexican drug cartels are quietly filling the void in the nation’s drug market created by the long effort to crack down on American-made methamphetamine, flooding U.S. cities with exceptionally cheap, extraordinarily potent meth from factory-like “superlabs.”

Although Mexican meth is not new to the U.S. drug trade, it accounts for as much as 80 percent of the meth sold here, according to the Drug Enforcement Administration. And it is as much as 90 percent pure, a level that offers users a faster, more intense and longer-lasting high.

“These are sophisticated, high-tech operations in Mexico that are operating with extreme precision,” said Jim Shroba, a DEA agent in St. Louis. “They’re moving it out the door as fast as they can manufacture it.”