The Garfield County Sheriff's Office has issued a warning about hazardous duct-taped "river bottles" turning up on river banks.
Fourteen bottles were found in the Roaring Fork River on Jan. 24, and since then, more than 50 have been found in three counties: Garfield, Eagle and Pitkin.
The bottles -- described as sealed 12-ounce hard plastic bottles wrapped in duct tape -- contain flammable, corrosive materials that are "hazardous to human health."
Sgt. Joe Gasper with the Basalt Police Department told 9NEWS the initial thought is these bottles could be associated with meth.
The substance inside the bottles is a blue and purple liquid with a solid, salt-like substance on the bottom.
If encountered, do not move, touch or open the bottles. Instead, note the location and immediately contact local law enforcement.
The Colorado Bureau of Investigation, Colorado State Patrol Hazmat team, Bureau of Alcohol, Tobacco, Firearms and Explosives, Drug Enforcement Administration are investigating.