SAN FRANCISCO - Federal agents said Thursday they shut down a factory that made marijuana-laced barbecue sauce, chocolate-covered pretzels and other "enhanced" snacks intended for medical users of the drug.

The Drug Enforcement Administration said it arrested three people Wednesday and was looking for a fourth who operated Oakland-based Tainted Inc.

Agents also seized 460 marijuana plants and other laced products including candy bars, cookies, marshmallow pies, ice cream, peanut butter, jelly, energy drinks and "Rice Krispy treats."

Tainted Inc. was launched by Michael Martin, 33, of El Sobrante as a small operation that made laced chocolate truffles. When it was raided Wednesday, the company was shipping products to medical marijuana dispensaries throughout California and in Seattle; Vancouver, British Columbia; and Amsterdam.

Authorities said the operation also had ties to Los Angeles pot clubs and believe it has ordered four tons of chocolate over the past two years to make marijuana-laced candy.

Those arrested were Jessica Sanders, Michael Anderson and Diallo McLinn. Martin is a fugitive, authorities said.

The raids of the factory and four Bay Area houses came after a two-year investigation and growing police concern that the legalization of medicinal marijuana in several states has caused a proliferation of large-scale marijuana-lacing operations.

Laced snacks are often more potent and longer lasting than smoked marijuana. Federal authorities contend that marijuana is an illegal drug, no matter how it used or who uses it, and they don't honor the state laws.

"This appears to be represent, once again, the federal government taking umbrage with the fact that California has legalized medical marijuana for medical patients," Sanders' attorney, Randolph Daar, told the San Francisco Chronicle. Lawyers for McLinn and Anderson had no comment.

A call to the company Friday was not returned.

Several people who ran a marijuana-lacing operation called Beyond Bomb that produced such products as Stoney Rancher, Rasta Reese's and Keef Kat pleaded guilty this year in Oakland federal court to marijuana charges. Beyond Bomb's founder Kenneth Affolter was sentenced to nearly six years in prison.

"These items could have harmful effects on a user, especially the unsuspecting ones," DEA agent Javier Pena said. "We will continue to shut down these production lines, one marijuana-candy factory at a time."

(This version CORRECTS name of agency to Drug Enforcement Administration.)