Crews battling a house fire last week may have inadvertently caused nearly two-million litres of diluted sewage to pour into the Assiniboine River.

The City of Winnipeg confirms 1.8 megalitres of the diluted sewage — more than two-thirds the volume of an Olympic swimming pool — flowed into the river on Feb. 5 near Ferry Road. The surge lasted at least three hours from the time an overflow alarm went off at about 7:45 p.m.

The water firefighters used to douse a nearby blaze on Roseberry Street south of Ellice Avenue likely caused the leak, the city said.

The cause of the fire remains under investigation.

The city says it reported the wastewater discharge to Manitoba Sustainable Development the day of the incident.