Residents warned to avoid brook and ponds in Shrewsbury and Northborough after sewage overflow

State officials advised people to stay away from a brook in Shrewsbury and two ponds in Northborough until at least Monday as a precaution after a sewage system overflowed with rainwater.

Water from the week’s rainstorms dislodged a manhole cover, and untreated sewage mixed with rainwater spilled into Hop Brook in Shrewsbury, which flows to Smith and Thayer ponds in Northborough.

Drinking water should not be affected, said Ed Coletta, a spokesman for the state Department of Environmental Protection.

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“We’ll be doing some testing, some water sampling, on Monday, and we’re hoping that by then we’ll have a better idea of what the bacteria levels are,” Coletta said.

Hop Brook in Shrewsbury, which is usually a few feet wide at most, carried much of the overflow water, Coletta said.

By this morning, the flow had slowed, said Shrewsbury Town Manager Daniel J. Morgado said.

“I was there just before noon, and it was just – barely a trickle. By now we should be through with it,” he said early this afternoon.

The brook runs through wooded areas, not residential neighborhoods, and is not usually a site for canoeing, swimming, or fishing, Morgado said. Officials posted a notice on the town’s website asking the public to avoid making contact with the water, but did not think physical signs near the brook were necessary, Morgado said.

The town’s sewage system last overflowed in March 2011.

“This weather we’ve had in the last couple weeks had just tested the system to its maximum capacity,” Morgado said.