A boil water advisory has been issued for the entire City of Winnipeg after low levels of bacteria, including E.coli, were detected in water samples Tuesday.

The Winnipeg Regional Health Authority initially issued the advisory for areas east of the Red River.  But after discussing the lab results with experts, city officials decided to extend the advisory to the entire city “out of an abundance of caution,” Mayor Brian Bowman told a news conference.

Bacteria, including coliform and E.coli, were found in six water samples, city officials said.

Five of the six positive tests were east of the Red River, and one was in the city’s southwest.

Bowman said the city decided to extend the boil water advisory to the entire city because the water system is inter-connected.

Bowman said he hopes that the results were “false positives” and the city will be re-sampling the water supply. Those results are expected Wednesday afternoon.

In the meantime, Winnipeg residents must bring their water to a rolling boil for at least one minute before it is used for drinking, cooking, brushing teeth, making ice and preparing infant formula.

If boiling water is not feasible, residents are urged to use bottled water.

The health authority says it is not necessary to boil water for other household purposes, such as washing dishes and doing laundry.

Additional information and updates will be available on the city’s website. City officials are set to provide an update on the boil-water advisory Wednesday at 7:30 a.m. local time.

As news of the boil-water advisory came down, many residents rushed to stores to stock up on bottles of water.

Unusual sampling

Geoff Patton, acting director of Winnipeg’s Water and Waste Department, said the water testing results were puzzling because some showed the presence of both coliform and chlorine, which can’t go together.

This suggests the samples may be inaccurately detecting bacteria.

“It’s hard to understand – we see clean results upstream and downstream of the locations, and then we see this unusual sampling,” Patton said. “So what has happened? That is what we’re looking to do.”

Winnipeg’s water is transported from Shoal Lake, Ont., which is located approximately 150 kilometres east. The water is treated at a plant near the Deacon Reservoir just east of Winnipeg.

Recent water troubles

Winnipeg, which is home to approximately 700,000 people, has previously dealt with water problems.

In 2013, the city issued a boil-water advisory for one neighbourhood, only to lift it when no E. coli contamination was detected.

A year later, Winnipeg officials said that the cause of discoloured water coming from residential water taps was due to manganese from Shoal Lake and water treatment plants.

The levels of manganese, which is used as a coagulant, were not harmful. However, the city said it would clean approximately 2,500 kilometres of water pipes.

Last winter, frozen pipes left thousands without running water for weeks.

Part of the problem is an aging infrastructure strained by cold winters and hot summers.

Manitoba NDP MP Niki Ashton said the city’s latest troubles sound an alarm.

“And I hope the federal government can hear it, because this does speak to the need for federal investment in infrastructure, and there’s nothing more important than having safe drinking water,” she said.

A spokesperson for the federal infrastructure minister said that Ottawa has already invested billions in Canadian water projects. It’s up to the provinces and cities to prioritize how that money is spent, the spokesperson said.

Winnipeg authorities issued a boil water advisory

With a run on bottled water earlier in the day late night shoppers were were greeted with empty shelves after Winnipeg authorities issued a boil water advisory after a E.coli positive test Tuesday, Jan. 27, 2015. (John Woods / THE CANADIAN PRESS)

When to boil

When not to boil

Winnipeg water boil advisory

With a run on bottled water earlier in the day late night shoppers were were greeted with empty shelves after Winnipeg authorities issued a boil water advisory after a E.coli positive test Tuesday, Jan. 27, 2015. (John Woods / THE CANADIAN PRESS)

With files from CTV News’ Jill Macyshon and The Canadian Press