DENVER -- Denver is starting work on becoming the first city in the nation to allow marijuana clubs and public pot use in places such as coffee shops, yoga studios and art galleries.

Voters narrowly approved the "social use" measure last November. But the ballot proposal didn't spell out many rules for how the marijuana could be consumed, beyond saying that the drug can't be smoked inside and that patrons must be over 21.

A workgroup made up of Denver business owners, city pot regulators and marijuana opponents starts work Wednesday on suggesting regulations.

The state Liquor Control Board already has decreed that no businesses with a liquor license can allow marijuana use. That leaves it to restaurants that don't serve alcohol and other event spaces.

There's no deadline for Denver to finalize rules.