LOS ANGELES (AP) — A short walk from police headquarters in the heart of downtown Los Angeles, a cluster of bustling shops are openly selling packaging and hardware that can be used to produce counterfeit marijuana vapes that have infected California’s cannabis market.

Bootleggers eager to profit off unsuspecting consumers are mimicking popular, legal vape brands, pairing replica packaging churned out in Chinese factories with untested, possibly dangerous cannabis oil produced in the state’s vast underground market.

The result: Authentic-looking vape cartridges sold by unlicensed dispensaries and delivery services, along with rogue websites.

The deceptive rip-offs on the street could be linked to an emerging public health crisis. Hundreds of people across the U.S. have been sickened, mainly by vaping cannabis oil, and six deaths have been reported. Public health officials aren’t sure what’s causing the lung issues, vomiting and other symptoms, but in California they say most patients reported purchasing vapes from pop-up shops or other illegal sellers that are a pipeline for counterfeit products.