E. coli was found Thursday in the water in Burlington, leading the Massachusetts Department of Environmental Protection to issue a boil water order.
The town said the bacteria had been found in three of 11 samples from its drinking water system.
"These bacteria can make you sick and are a particular concern for people with weakened immune systems," the town said in a statement.
People in Burlington should not drink or use tap water without boiling it for a minute first. The order will continue until further notice.
Town officials offered new details Friday, saying that the three water sample tests returned positive for E. coli on Thursday during routine testing. The city hasn't received any reports of illnesses associated with the bacteria.
It wasn't immediately clear what caused the contamination, and the city was retesting its system Friday, as well as examining water tank hatches by drone.
"I want to apologize for the inconvenience this has caused, and assure residents that we are doing our very best to correct it as soon as possible," Director of Public Works John Sanchez said in a statement.
Town eateries like the Chateau Restaurant say business had been picking up after most COVID-19 restrictions were lifted, but now this boil water order just adds one more thing to their plate.
"This whole year has been frustrating so we're basically used to frustration," Chateau manager Nikki Athansiades said.
At the Chateau, signs are posted on the door to warn customers that some items may be limited, and that they're unable to serve drinks like coffee or tea.
"This morning I ran over to Market Basket and grabbed a bunch of two liters of soda and tonic water and ice," Chateau manager Jeff Higgins said.
Other places like the Cold Stone Creamery in town were closed Friday because of the situation.
The town's Department of Public Works says the boil water order could last through the weekend.
"We'll continue to do sampling but it takes 24 hours to get the results so whatever we do today, we'll find out tomorrow afternoon. We'll do another round tomorrow," Director John Sanchez said.
Depending on how long this lasts, it could mean reservations for what's expected to be a busy Father's Day on Sunday at the Chateau may have to be cancelled.
"Unfortunately yes I definitely think if the town can't figure something out, we're going to be in tough water then," manager Jeff Higgins said.
The DPW director says if the tests come back negative this weekend, then it will be up to the state's Department of Environmental Protection to decide whether or not to lift the order. Until then, they're asking people to continue to boil any cooking or drinking water for at least one minute before using it.
E. coli can cause diarrhea, nausea, headaches, cramps, jaundice and fatigue, though those symptoms can be cause by other illnesses, the town noted. They urged anyone with those issues to contact their health care provider.
Anyone in Burlington with questions about the water system can call call Public Works at 781-270-1670 or the Board of Health at 781-270-1955.