The water quality at the upper beach at Hopkinton State Park returned to an unsafe level for swimming due to an increase in enterococci bacteria over the past week, according to water sample test results released Wednesday, while the water quality at the main beach remains unsuitable for swimming.

Last week, the bacteria level at the upper beach had returned to a safe level. Based on the testing of water samples on Tuesday, a warning was announced Wednesday by the state’s Department of Conservation and Recreation. Ingesting or becoming submerged in bacteria-laden water can lead to symptoms including diarrhea and stomach pains.

The enterococci bacteria level at the upper beach was 185, noted Health Department director Shaun McAuliffe in an email. The threshold is 61, which is about one-third of what was found in the sample.The level at the main beach was 99, according to the DCR data.

Beaches statewide have been experiencing high levels of bacteria in recent weeks during the time of year when they are in the greatest demand for recreation. One cause is the amount of goose droppings in the water.

Lake Maspenock remains safe for swimming.