REGINA -- The City of Regina is investigating how oil from the Co-op Refinery Complex ended up in the city’s wastewater system.

The refinery could be fined as result of the investigation.

"We will be continuing that investigation and looking to recoup any of our costs," City of Regina Director of Water, Waste and Environment Kurtis Doney said.

According to the City, on May 22, staff at the McCarthy Boulevard pumping station identified hydrocarbons in the wastewater collection system.

The Water Security Agency and Ministry of Environment were alerted immediately and testing confirmed hydrocarbons had been released into Wascana Creek.

"Despite our quick action, no municipal wastewater treatment plant is designed to treat for this type of event, however, the majority of the hydrocarbons were isolated in our lagoons," Doney said.

After receiving the testing results, the City informed downstream residents on Friday.

"It’s very important for the City of Regina to have the full information and to understand the risk, so that when we provide a response to the public, or to downstream users, that we can give them a sense of the risk and if any action is required," Doney said.

The City says no action is required by residents and maintains the risk to the public is low, which reiterates what the Water Security Agency and Co-op told CTV News Regina on Monday.

"With the information that we have today, it’s important to note that the risk remains low," Doney said.

The City believes that no damage was done to the wastewater treatment plant and a clean up is underway at the lagoons.

Testing is also continuing at the plant, at the affluent that leaves the plate and downstream.

"Those samples are submitted to a third party lab, it can take between two and 10 days to get the results, depending on the parameters that we’re looking for," Doney said. "Those tests will continue on at the direction of the Water Security Agency and we’ll continue to get more information regarding those tests.”

The City says the refinery has confirmed it was the source of the discharge and is responsible for notifying its regulator.

"The Co-op Refinery Complex has notified the City they are implementing short and long-term improvements to improve the quality of their waste water," Doney said.

Co-op says high winds resulted in sediments from a lagoon at the refinery being discharged into the sewage system.

Doney added he doesn’t believe there has been concerns of hydrocarbons in the water before this incident.