WINDSOR, Colo. (AP) — Some Weld County residents are asking why it took several days to close Windsor Lake to swimmers after initial reports that people were getting sick.

The Greeley Tribune reported Thursday the lake was closed on Monday after testing showed elevated levels of E. coli bacteria. The Weld County Department of Public Health and Environment has confirmed seven cases of a gastrointestinal infection called shigella. It can be caused by E. coli.

Windsor’s director of parks and recreation, Melissa Chew, said the town contacted county health officials after getting reports that people were getting sick. Crow said test results from samples taken on Friday were not reported to the town until Monday.

An arts festival was held at the lake over the weekend.

“It takes 24 hours to get test results back,” Chew said. “We did not get a call from the health department until Monday because they were closed on Saturday.”

Some residents want answers.

“My husband and I were there on Monday, and of course had been swimming in it,” said Leslie Nance of Severance. “Monday night I saw a Facebook post that said the lake was closed, and they were talking about E. coli and people getting ill.”

Kelly Campbell, an official with the health department, said it wasn’t clear what caused the shigella.

“There are a lot of different types of bacteria outbreaks that can cause it in agricultural bodies of water,” Campbell said. “Windsor Lake is an agricultural body of water. We don’t know, but with the rain over the past few days it may have stirred something up in the soil.”

Shigella can cause diarrhea and dehydration. Officials said anyone who suspects they may be sick should visit a doctor and drink plenty of water to offset dehydration.

(© Copyright 2012 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)