Mayor Brian Bowman said it could be Thursday afternoon before yet another round of tests was completed and people would be able to safely drink the water without boiling it first.
"I'm pleased to advise that the testing we've conducted in the last 24 hours has come back negative, which means, according to our experts ... (the original samples) are false positives," Bowman said at an update.
Under provincial guidelines, a boil-water advisory cannot be lifted until two consecutive retests come back clean.
"The province has the authority to lift the precautionary boil-water advisory. Once we receive that indication, we'll obviously notify Winnipeggers as quickly as possible."
The advisory was put in place Tuesday after coliform and E. coli showed up in extremely low levels in six of 39 water samples taken during routine testing.
Businesses and residents were being told that tap water was safe for bathing and laundry, but were advised to boil it for at least a minute before drinking it.
Officials said the testing and re-testing was being done as quickly as possible. Samples need time to grow in the lab because they are bacteriological tests.
Once the advisory is lifted, the city will turn its attention to figuring out what happened.
Geoff Patton, acting director of Water and Waste Department, said the same worker took all six of the suspect samples, but what went wrong is still a mystery.
"We've evaluated all of our operations systems. We've evaluated the protocol, the procedures. We spoke to the lab. We spoke to the tester. There is nothing that is showing up as anything that would lead to these issues," he said. "We need to look at several other issues and we are going to be doing that over the next little while."
Many residents had already appeared unfazed by the earlier test results that showed E. coli and coliform.
Most coffee shops and restaurants were open, although some menu items were not available. Schools were also open, but some warned students to bring bottled water because the water fountains were closed. It was business as usual at city pools.
Hospitals saw no sign of a spike in illness, and surgeries and other services went on as usual.
Dave Bilyk, a homeowner in south Winnipeg, said his family was coping well and did not feel the need to rush out and buy bottled water.
"We boiled about five or six litres worth and that way we can run it through the Keurig (coffee maker) for coffee in the morning and we can use it for brushing our teeth and so on," he said Tuesday night.
Brian Wills said he, his wife and four children were not too worried. He even used a bit of tap water to brush his teeth — something the city advised against. And he was pleasantly surprised to find his favourite coffee shop was still brewing Wednesday morning.
"I often buy my coffee out, so I would hope that they're doing something with their water to not get (people) sick."
Brent Neill said he drank a lot of the water just before the advisory was issued.
"I was at the YMCA and drinking water from the water fountain ... but I didn't think too much of it."
"This morning was the only time I was a little annoyed because Starbucks was closed. That's the only thing that has affected my day-to-day life and routine."
Bowman urged residents to heed the precautions, but at the same time remain calm.
"Take a deep breath. Boil the water. Get some bottled water if you can't boil it, and hopefully (Thursday) we'll be able to provide you with better news."