AMHERST — For the second time this summer, Puffer’s Pond is being closed to swimmers after water samples showed higher than normal levels of E. coli bacteria.

According to a notice posted to the town website, the presence of the bacteria is linked to the heavy rain the region received Monday and Tuesday, which caused runoff into the water.

The samples were taken Wednesday from both the main beach off State Street and the north beach, closer to Mill and Summer streets.

Using precautions from the town Health Department and the Massachusetts Department of Public Health, town officials are advising people not to swim in the pond, and have placed prominent postings at the site.

Additional samples will be taken Monday, with results expected the following day.

The pond was previously closed June 25 through July 2.

The decision to close the pond to swimmers means that one of themost popular places in town where people stay cool will not be available during what is expected to be a sunny and warm stretch of weather.

Last weekend, in the midst of very high temperatures and high humidity, the town extended the hours and offered free open swimming at the two town swimming pools at Mill River and War Memorial. Even with the free alternatives, Puffer’s remained busy.

On Saturday afternoon, July 20, police discovered at least 30 swimmers, mostly teenagers and college-age people, who had climbed onto the cliff to dive into the pond, along with others sunbathing on top of the dam.

That day also served as a test for the new parking rules near the pond, with police discovering some cars parked across the bicycle lane. The lane is not marked as such and there are no “no parking” signs.

Town Manager Paul Bockelman said this was the first time there was stress on parking at the beach, which revealed a need for more timely and consistent enforcement. Police will patrol the area throughout the rest of the summer.

According to the Centers for Disease Control and Prevention, although some strains of E. coli are harmless, others can cause sickness such as diarrhea, urinary tract infections, respiratory illness, pneumonia and other illnesses.

Updates about the status of the pond will be put on the town website and shared on Amherst’s social media channels.

Scott Merzbach can be reached at smerzbach@gazettenet.com.