The move comes after Friday's release of a study by the U.S. Geological Survey that found the naturally occurring radioactive isotope in 24 private wells and one public well. Polonium-210 is known to cause cancer in humans.

Fallon farmer Bret Sorensen said he began dumping 6,000 gallons of milk Friday morning at the request of the Dairy Farmers of America, the cooperative to whom he sells milk.

"A milk quality-control person from the DFA ... said one of the wells on the dairy was compromised and it would be best to quit taking our milk," Sorensen told the Reno Gazette-Journal. "I agree with (the) decision. It is better to be safe than sorry."

Dr. Anette Rink, a supervisor at the Nevada Department of Agriculture, said she sent milk samples to an FDA laboratory in Massachusetts to be tested and she expects results back by Monday.

Rink said milk is not normally sampled for polonium-210, and she doesn't expect the Fallon samples to test positive for the isotope.

All 23 dairies around Fallon sell their milk to the DFA cooperative, which in turn markets the milk to Model Dairy in Reno and to plants in Northern California. No other dairies were part of the random testing of wells around Fallon.

Concentrations of polonium-210 found in the 25 wells ranged from less than 0.1 to 67.7 picocuries per liter. Thirteen of the wells had amounts greater than 15 pCi-L, which is the federal EPA's maximum contaminant level for gross alpha radioactivity in public wells.

The EPA has no individual standard for polonium-210 levels in public water supplies and does not regulate private wells.

Officials said they think the elevated levels stem from natural causes, and there's no known health risk at this time. Research to determine whether there's a risk is being conducted by state and federal agencies.