The swimming pond at Lake Elmo Reserve Park was closed temporarily Thursday after several swimmers reported illnesses, said the Pioneer Press.
The Cryptosporidium organism, which causes diarrhea and other gastrointestinal symptoms, is believed to be the cause of this outbreak, said parks director John Elholm to the Star Tribune.
In order to eradicate the parasite, the pond needs to be treated with chlorine, a process which will last until Friday afternoon, said the Star Tribune.
Although the exact cause and source of the outbreak are not known, all of the swimmers who reported symptoms swam at the Lake Elmo pond, said the Pioneer Press.
"Park visitor safety is our main concern," said Elholm to the Star Tribune.