AMHERST - Tests conducted on town water at 10 sites Friday showed no evidence of contamination by coliform or E. coli bacteria, said Robert Pariseau, director of water services.

He received word from the state Department of Environmental Protection at 4:05 p.m. Saturday that it would not issue an order for Amherst residents to boil water before using it, he said.

On Thursday, disease-causing E. coli bacteria was detected in a routine sample taken in North Amherst, and there were two positive tests for coliform bacteria, one on the University of Massachusetts campus and another near it. Pariseau ordered an increase in chlorination to disinfect the water and ordered 10 repeat tests at those three sites and seven in their vicinities, he said.

On Saturday, he learned that all 10 samples had tested free from any bacteria, he said.

Pariseau attributed the detection of E. coli during the previous test to a sampling error.

"We had plenty of chlorine, so we never should have had E. coli there," he said.