(Reuters) - A Colorado farming town on Saturday ended restrictions put on the local water supply this week after it warned residents to avoid drinking the town’s water because THC, the psychoactive agent in marijuana, was found in a feeder well.

The local sheriff said a criminal investigation has been launched to look into possible tampering of the well in Hugo, a town of about 800 people some 90 miles (145 kms) southeast of Denver.

"The Colorado Bureau of Investigation has just reached out to us and advised that samples taken from Well #1 and throughout town are NEGATIVE for THC," the Lincoln County Sheriff's Office said on its Facebook page on Saturday.

The water restrictions were lifted on Saturday morning, Lincoln County Public Health said in a Facebook post.

"The municipal water in the Town of Hugo is SAFE," the post read.

The county health department said in an alert on Thursday that residents should avoid drinking, cooking or bathing with the town’s water for at least 48 hours after a field testing kit showed the possible THC contamination.

Peter Perrone, a chemist and owner of the state-licensed cannabis testing facility, Gobi Analytical in suburban Denver said in an interview that it is virtually impossible to find THC in water in concentrated levels because cannabinoids are not water soluble.

(Reporting by Jon Herskovitz; Editing by Nick Zieminski)