The city of Ovalle in Chile’s Coquimbo region suffered a massive outbreak of norovirus in the first week of September, infecting 3,000-plus residents, due to insufficient chlorine levels in the potable water supplied by water utility Aguas del Valle, according to a release by the regional health authority Seremi.

“What happened is that 24, 36 and 48 hours before the outbreak on September 3 there was a drop in chlorine levels and the water was contaminated by norovirus from the Limarí river… which is why we are carrying out a report into the role of the sanitation company,” said Seremi head Osvaldo Iribarren.

The authority said that the result of the report will be passed to the public prosecutors office in compliance with article 315 of the penal code.

Aguas del Valle, for its part, said the health authority’s chlorine measurements are “not trustworthy” as its methods “did not comply with industry protocol” and the tools used were “totally obsolete.”

The water utility maintains that chlorine in the water supply and at its plant has been above stipulated levels, and that there is no evidence implicating the firm in the norovirus outbreak.