DENVER (Reuters) - Residents of a small farming community in eastern Colorado have been warned to avoid drinking the town’s water after THC, the psychoactive agent in marijuana, was found in one of its feeder wells, authorities said on Thursday.

A thriving marijuana plant is seen at a grow operation in Denver, Colorado December 31, 2013. REUTERS/Rick Wilking/File Photo

A public works employee in Hugo, a town of about 800 people 90 miles southeast of Denver, detected the chemical and health officials believe it is “marijuana THC-related,” the Lincoln County Sheriff’s Office said in a Facebook posting.

“At this time, investigators are assessing the situation with state and federal authorities,” the sheriff’s office said. “Bathroom usage is still safe, but until more information is known to us, out of an abundance of caution, avoid drinking Town of Hugo water.”

Susan Kelly, the county’s public health director, said there were no reports of anyone falling ill or otherwise being affected by the tainted water.

Colorado allows both medical and recreational marijuana use. But it was unclear how THC got into the water, as there are no legal marijuana cultivation sites or dispensaries in the area, according to the Colorado Department of Revenue, which regulates the state’s cannabis industry.

Captain Michael Yowell of the sheriff’s office said there was evidence that the well was tampered with, and that the FBI and Colorado Bureau of Investigation have joined the probe.

The initial screening was done with a “field testing kit,” Yowell told reporters, and the state health department would conduct more through testing. The level of contamination detected was not specified.

The Lincoln County health department said in an alert that residents should avoid drinking, cooking or bathing with the town’s water for at least 48 hours.

“The contaminated well has been identified and shut down and the lines are being flushed,” the alert said. “Fresh water will be coming into town for the public as soon as possible.”

Peter Perrone, a chemist and owner of the state-licensed cannabis testing facility, Gobi Analytical in suburban Denver, said he was skeptical of the reports.

“It’s virtually impossible to find THC in water in concentrated levels because cannabinoids are not water soluble,” Perrone told Reuters in a telephone interview.

Yowell said he understands that some are questioning how THC could be found in the water, but that does not explain why the tests came up positive for the chemical.

“I wouldn’t be doing my job for the community if we just wrote this off,” he said.