The mystery began when a company that had been testing its workers for drugs tried to test the town's water and found a positive THC result, Lincoln County sheriff's Capt. Michael Yowell said. Authorities invalidated that result Saturday.

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Samples of water in Hugo, Colorado, test negative in lab for THC

Lab tests were done after field tests had showed a positive result, now believed to be false

CNN  — 

A Colorado town’s marijuana-in-the-water mystery didn’t check out after all.

Laboratory testing showed there is no THC – the principal psychoactive chemical in cannabis – in the town’s water supply, contrary to what field tests had shown earlier this week, the Lincoln County Sheriff’s Office said Saturday.

The announcement brought the curtain down the town’s two-day water advisory, during which its 700 residents were asked not to drink, shower with or cook with the tap water.

“We are happy to announce that the water advisory is canceled immediately,” the sheriff’s department said.

Why did investigators think THC was in the water to begin with? It’s a tale that begins with an employer’s drug tests.

A company in town was testing its employees for drugs with a field-testing kit, but was noting some discrepancies in the results. The company then tested the tap water, anticipating that it would serve as a control for further tests by showing what an absolute negative result would look like, Lincoln County sheriff’s Capt. Michael Yowell said.

But the field kit indicated the tap water was positive for THC, Yowell said.

The company told the town’s public works department, which then used field tests throughout the water system and found THC-positive results in one of the town’s five water wells, as well as other locations in the system.

The mystery deepened when workers found evidence that the well with the positive result had been broken into, Yowell said. The department called the sheriff’s office, leading to a full-blown investigation.

The Colorado Bureau of Investigation was called to collect samples for laboratory tests on Thursday. Health officials said no one had complained of adverse symptoms from drinking the water, but they issued the advisory out of caution, saying short-term ingestion could impair coordination and increase anxiety and paranoia in the worst case.

In the end, the lab tests were negative – and investigators believe the field test results were false, the sheriff’s department said.

The break-in at the well still hasn’t been solved.

“The criminal investigation into damage on well #1 structure will continue,” the sheriff’s department said Saturday on Twitter.

CNN’s Ana Cabrera, Emanuella Grinberg, Steve Almasy and Salim Essaid contributed to this report.