Investigators in Ostersund, Sweden, say they traced a cryptosporidium outbreak that has sickened more than 11,000 residents to a multifamily dwelling in the city’s Odensala neighborhood

Ostersund environmental head Jari Hiltula told Swedish news agency TT,

"We’ve found high levels of the parasite in the connection to this source. We’ve handed over the information to the police who are responsible for the investigation. A property owner will also be contacted."

The parasite may have entered the city’s water supply through a sewage line mistakenly connected to a rainwater drainage system, the report said.

"It looks like the sewage pipe wasn’t connected properly," said Andrew Sorensson, an environmental crimes investigator with the Ostersund police.