AMHERST — For the first time this summer, people are being advised not to swim at Puffer’s Pond due to high levels of E. coli bacteria.

Signs are being posted at the State Street site and a notice is also on the town website.

While the pond regularly showed E. coli levels above state safety standards in previous summers, this spring and summer’s tests had been acceptable until this week.

Assistant Town Manager David Ziomek said Tuesday that the recent wet weather, coming just before the weekly testing, was concerning.

The town website explains the problem with thunderstorms and rainy days, noting “large rainstorms can wash dog or bird feces into the water. Farm manure runoff and aging sanitary sewer pipes leaking sewage can also contribute to contamination.”

The water quality is examined throughout the swimming season, from Memorial Day to Labor Day, with the samples tested at a lab at the town’s wastewater treatment plant.

Puffer’s Pond has drawn its usual crowds of swimmers and sunbathers this summer, such as on Independence Day weekend, when police responded to disputes over loud music and the unauthorized use of grills. Last weekend, police were contacted after youths were found jumping from the cliff, an area that is supposed to be off limits due to safety concerns.

Puffer’s Pond remains a free option in addition to the full-size municipal swimming pools, Mill River and War Memorial, which both have fees for entry. But there are no lifeguards at Puffer’s.

The town has been examining the condition of the pond and has an improvement plan in process, with a need to remove excess sediment in the pond and deal with the various trails that are deteriorating.

Ziomek has said that typically bodies of water that are shallower and warmer have an issue with E. coli bacteria.

The Amherst Public Health Department makes the decision on whether to close the site for swimming. People with questions can contact health officials at [email protected] or 413-259-3077.

The next test results will be posted July 22.