DENVER (AP) — Investigators have raided about 30 homes and warehouses throughout the Denver area as part of a multi-state investigation into the illegal distribution of marijuana outside Colorado.

A law enforcement official with knowledge of the investigation says dozens of people were arrested in Thursday’s raids. The official says the investigation began after residents living near the grows complained about the smell of weed and involves people who moved to Colorado specifically to illegally grow marijuana for export.

The official wasn’t authorized to comment on the ongoing case and did so on the condition of anonymity.

At one home in a residential neighborhood, agents laid out confiscated grow lights on the lawn and driveway. In an industrial spot in Denver, large pot branches were stacked up outside a trailer.