Drug Enforcement Administration and FBI agents joined state and local agencies in a massive, coordinated raid of more than a dozen suspected illegal marijuana growing operations across the Denver metro area Thursday morning, federal officials said.

Drug investigators began serving judicial warrants to suspected drug trafficking locations following a lengthy investigation, said Deanne Rueter, spokeswoman for the DEA in Denver.

“There’s quite a few in Thornton,” Rueter said. “A lot of cities are involved.”

Law enforcement agencies across the metro area are involved, including Denver, Aurora, Thornton, Commerce City, Broomfield police and sheriff’s investigators from at least Jefferson and Arapahoe counties.

Rueter declined to give specific details about the total number of homes and businesses that are being raided. She said she does not know whether law enforcement officers are making drug-related arrests, but that the situation is an ongoing criminal investigation.

Just before 11 a.m., agencies were still going house-to-house serving warrants to suspected locations across the metro region.

Television footage showed pot plants laid out in the driveway of a home in a middle-class subdivision in the suburb of Thornton. Agents in hazmat suits were walking around the front of the home as three people sat handcuffed on the curb. A group of neighbors, some out with their dogs, gathered on a corner to watch.

In June of 2017, a massive bust resulted in a Denver grand jury indicting 62 people accused in a marijuana trafficking organization that reaped millions of dollars by illegally growing pot and selling it out of state for four years.

At the time, the bust was the largest in Colorado since recreational marijuana was legalized in 2014. The bust was indicative of law enforcement cracking down on gray market growers exporting their products across state lines.

On Thursday morning, Rueter said she was unable to characterize the size of the raid that involved residences across the state.

The Associated Press contributed to this report.

This breaking news story will be updated as new details are available.

Marijuana plants spread out on the driveway of a home raided this morning by federal and local police. I’m told this investigation involves illegal marijuana trafficking outside of Colorado — which is illegal anyway you slice it. This is in Thornton. pic.twitter.com/qqS8oqD0T9 — Jace Larson Denver7 (@jacelarson) August 9, 2018