Early Wednesday morning, 28,000 litres of diesel from a generator at a Longueuil waste water treatment plant started leaking into the St. Lawrence River.
The provincial environment ministry was notified just before 9:30 a.m. ET.
Urgence-Environnement officials arrived on the scene about six hours after the after the initial leak.
The city issued a statement saying the water was safe to drink Wednesday evening.
On Thursday morning, the city issued another statement telling residents in some areas of Longueuil and surrounding communities not to drink the tap water.
Longueuil Mayor Caroline St-Hilaire said the advisory was introduced as a precaution after complaints from residents. She said there was no indication the water supply was unsafe. Only traces of contaminant were detected.
Who is affected?
Residents in the areas of Saint-Hubert, Vieux-Longueuil, Boucherville and Saint-Bruno-de-Montarville should not drink water from the municipal supply until further notice.
The Marie-Victorin and Riverside school boards have also issued preventative bans on drinking municipal water in their institutions.
Drinking water in Brossard and St-Lambert, as well as Lemoyne and Greenfield Park, is not affected, according to the City of Longueuil.
The city has set up distribution centres to hand out water to residents at the following locations. They opened at 3:00 p.m. ET.
Residents who go to one of the fire stations on the list must bring their own clean containers.
- 1100 Marie-Victorin St.
- Chalet St-Charles, 195 Chateauguay St.
- Colisée Jean-Béliveau, 1755 Jacques Cartier Boul. East
- Olympia Arena, 2950 Dumont St.
- Fire station 31 in the Le Moyne sector, 2205 Saint-Georges St.
- 6355 Maricourt St.
- Rosanne Laflamme Sports Centre, 7405 Terrasse du Centre
- 4130 Grande Allée St.
- Fire station 33 in Greenfield Park, 1510 Bellevue St.
- Pierre-Laporte Sports Centre, 490 Chemin du Lac
- Centre communautaire Saint-Louis, 220 Claude-Dauzat St.
- Fire station 43 in Brossard, 3300 Blvd. Lapinière
- Les Ailes de la Mode parking lot (as of 6 p.m.)
- Centre Marcel-Dulude, 530 Clairevue West Boul.
- Fire station 41, 55 Argyle St.
- 100 Murano St.
- 1850, Blvd Marie-Victorin (from 6:30 p.m. until 11 p.m.)
What will happen if you drink the water?
The smell and taste of the water is likely to cause the most immediate physical reaction, according to water experts.
Symptoms like diarrhea and vomiting may be a side effect of ingesting the water, said Marc-André Lemieux from Montérégie public health.
However, the average healthy adult, or even an elderly person, should not suffer ill effects, even if the water smells or tastes like diesel.
McGill University professor Ronald Gehr says the average person would have to drink a significant amount of straight diesel to have serious health consequences.
Most people would likely throw up before they got to that point, he said.
What is safe?
Citizens should avoid brushing their teeth using the water, according to Montérégie public health.
Ice cubes and drinks made with the water should be thrown out.
Showering and washing with the water is fine, said Longueuil Mayor Caroline St-Hilaire.