A thin film is forming on parts of Belle River after thousands of dead fish floated to the surfaced last Friday.
The Essex Region Conservation Authority (ERCA) told CBC Windsor that it's up to residents to clean up the carcasses in front for their property.
Jennifer Poisson, whose home backs onto the river is not happy about it.
"Take a look around, the number of fish — they`re bloated," she said. "They're huge. They want us to clean this up? I don't think so."
ERCA suspects there could be several causes for the deaths, including storm runoff with untreated sewage from a record breaking rainfall early last week.
Another cause could be the sudden drop in temperature of the water, also from the rain storm.
The Ministry of Natural Resources is looking into what could have caused the deaths. Results from a water sample are expected later this week.