“If the investigation leads to a prosecution, the penalty will be very, very high,” said Christer B. Jarlås, an environmental prosecutor, to the TT news agency.

Police are following the work being carried out to track how the Cryptosporidium parasite ended up in Östersund’s drinking water.

Once the work is completed, the police will conduct their own investigation to survey exactly where procedures broke down and who is responsible.

“A stomach parasite that makes people and animals sick shouldn’t be released and it absolutely shouldn’t end up in municipal drinking water. What has happened gives reason to believe that, due to carelessness, one or several individuals didn’t have control of their operations and as a result caused this contamination,” said Jarlås.

Jarlås, who works for the local office of environmental and workplace crimes division of the Swedish Prosecutor Authority (Åklagarmyndigheten), launched a preliminary investigation into possible environmental crimes after test results revealed that the intestinal parasite Cryptosporidium was present in Östersund’s drinking water.

More than 2,000 residents have taken ill after ingesting water from the city’s water supply, many suffering from diarrhea, vomiting, and severe stomach cramps.

City officials continue to hunt for the source of the leak. The parasite has been detected in water heading into the city’s water supply from the Storsjön lake as well as in water heading out of a local water treatment facility.

According to local media, rumours about the possible source of the parasite are running rampant among Östersund’s residents.

One anonymous water expert told the local Östersunds-Posten newspaper that one of the causes may be that the city’s waters system intake and outtake points in Storsjön are too close to one another.

Residents of Östersund, roughly 50,000 of whom are connected to the municipal water system, can expect to have to boil tap water for several weeks, an expert with the Swedish Institute for Infectious Disease Control (Smittskyddsinstitutet) told the TT news agency.

Once the source of the parasite has been found and shut off, it will take at least a month before it’s possible to drink water directly from the tap.

The health official referenced a similar outbreak in the city of Milwaukee in the United States, in which it took two months before water was safe to drink without boiling.