LINCOLN COUNTY, Colo. (CBS4) – The water supply in a small Colorado town was found to be tainted with THC, the main chemical in marijuana, and there are signs someone may have deliberately put it there.

Everyone in the town of Hugo, on the eastern plains, has been warned not to drink the water.

It was a company performing a routine employee drug test that first alerted law enforcement to the problem on Thursday — unknown levels of THC present in Hugo’s water.

“A vial of tap water was used to demonstrate what should have been an absolute negative result, however, when that tap water was tested, a positive indicator for THC was detected,” said Captain Michael Yowell of the Lincoln County Sheriff’s Office.

The sheriff’s office said half a dozen more tests showed the same, puzzling result. Then, a public works crew found a well house had been tampered with.

“It showed that there were signs of possible forced entry into the raw water system,” Yowell said.

Well house one is no being guarded around the clock and is considered a crime scene.

Not knowing exactly what’s in the water, or, how it got there, health officials told residents not to drink it until the system can be flushed in a matter of days.

“Our primary focus of course in the town of Hugo, and throughout Lincoln County, is on the health and safety of our residents,” said the Lincoln County Public Health Director, Susan Kelly.

Jennifer Barsi bought as much bottled water as she could find on Thursday.

“We received the announcement when I was in the grocery store. I was in there about 10 minutes and in that amount of time, people had rushed in and sold out of the water,” said Barsi.

While an area hospital reports no one has gotten sick, people in Hugo are taking the possibility someone deliberately contaminated their water very seriously.

“This causes real concern, because if it happens in Hugo, Colorado, it can happen any place,” said resident Maye Gene Lee.

The well remains closed as investigators await more conclusive test results from the Colorado Bureau of Investigation.

The Salvation Army will arrive in Hugo Friday morning to distribute bottled water.