The water was immediately decontaminated and retested that day.
Southeastern Water Authority told FOX61 that the results came back on Friday were negative for E.coli but still positive for total coliform. The tanks were again decontaminated and retested.
Total coliform very rarely causes illness in humans and at the very most one might feel nausea.
"Since the E.coli was not positive the second time around there was really no requirement to be a boil water advisory but because we had the two incidents back to back, we decided along with the state that we should do the boil water advisory, just in case, its mostly precautionary," Southeastern Water Authority General Manager Josh Canslar.
A reverse 911 phone call with the warning was issued Monday.
Officials say that only 300 people are affected due to most of North Stonington getting their water from wells. The majority of people affected are near the center of the town.
"They only really need to worry about water they consume," Canslar said. "It's okay to bathe, do your laundry, that kind of thing."
Resident Katrina Fedors said her family immediately got bottled water but incidents like this are concerning for neighbors with kids or the elderly.
"If they don’t have somebody to rely on, they might not be able to go out to the supermarket and get bottled water," she said. "Elderly people too are more likely to get sick, they can’t fight off infections as well."
Fedors said this isn't the first time there have been water issues in the community and she's hoping it gets resolved faster that in the past.
Officials say that results were most likely a fluke and the expect to get the most recent test results back Wednesday or Thursday of this week.
They believe the heavy rains from the other week may be a contributing factor in the results.