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 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.”

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.

Captain Michael Yowell of the sheriff’s office 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.