Federal and Colorado police have busted two illegal marijuana farms on BLM land along and near the Lower Dolores River, according to the U.S. Attorney’s office.

The unrelated farms were found south of Gateway in Montrose County after two separate tips.

According to a press release, BLM rangers discovered the first illegal grow on Sept. 15 on the Dolores River corridor. The found more than 1,200 fully mature marijuana plants, many exceeding 8 feet tall, along with 465 pounds of dried marijuana and a rifle.

The rangers arrested four Mexican nationals who were on scene, and believed to working the grow site, according to the U.S. Attorney.

A second illegal grow site was discovered by the same rangers with the assistance of Mesa and Montrose County Sheriff’s offices on September 30 near the first site.

The press release said that there was evidence of “thousands of marijuana plants that appeared recently harvested with approximately 69.6 kilograms (153 pounds)of processed marijuana still on site.”

Law enforcement arrested one Honduran, and five Mexican nationals at the second grow site.

“This fall, Colorado has seen an explosion in the number and size of illicit marijuana grows on public land, which federal and state authorities are aggressively investigating and prosecuting,” said U.S. Attorney John Walsh.

The grow sites present environmental hazards as well, said Katie Stevens, of the BLM Grand Junction Field office.

“These grow sites impact public lands by destruction of native vegetation, hazardous materials, and significant trash,” Stevens said.

These marijuana grows and the subsequent investigation were conducted by the BLM, Drug Enforcement Administration (DEA), the Mesa County Sheriff’s Office, the Montrose County Sheriff’s Office, 7th Judicial District Drug Task Force, the U.S. Forest Service and the U.S. Immigration and Customs Enforcement (ICE) Homeland Security Investigations (HSI).