MANCHESTER — The public beach at Crystal Lake was closed to swimmers Tuesday due to elevated levels of E. coli bacteria, according to the city’s health department.

Public Health Director Timothy M. Soucy said elevated bacterial levels were identified in routine water samples taken on Monday. Water samples of other locations on the lake were OK. Anything above 88 E. coli per 100 milliliters of water is considered unsafe.

The two water samples tested at 387 and 152, Soucy said.

“We don’t know what the cause is,” he said. “It’s usually bather load (children in diapers) or bird or duck droppings.”

He said the water will be tested daily and the beach will be reopened when the bacteria count is at a safe level.

The last time the beach was closed because of high bacteria levels was in 2008.