Thousands of people in the South Yorkshire town of Thorne have been warned to drink or cook with tap water after "high levels of bacteria" were detected in the supply. Yorkshire Water said 3,600 properties had been affected in the community near Doncaster.
"High levels of bacteria have been detected in the local water supply, prompting us to issue the precautionary Do Not Drink advice which customers must follow until further notice," the firm said on its website.
Former Labour leader Ed Miliband said he was "very concerned" over the situation affecting the area which included neighbouring village of Moorends, which is part of his constituency.
The firm added that they had been "working through the night carrying out further investigations into the cause of the contamination; flushing the local water supply system and carrying out further quality tests".
The results of the tests are due back on the afternoon of 30 July, they said, at which point they would update customers.
Taking to Twitter, the MP for Doncaster North, said: "Very concerned for residents who can't drink water because of contamination in parts of Moorends. In touch with Yorkshire Water about their provision of water while problem is fixed. Also speaking to council."
On its Facebook site, Yorkshire Water said that they had provided 100,000 litres of bottled water and would continue to do so until the issue was resolved.
"We ask that customers only take what water they need and to help any vulnerable neighbours and friends. Although the water is not safe to drink, it is safe to wash in and for flushing toilets," they said.
Some of those customers complained on Facebook that people were taking more than their fair share of water bottles, leaving others including children and the elderly without enough to drink.
Caroline Simpson said she had seen people "with car boots full of water" while she had been unable to get any for her household of four, including two children. An old lady on her street had also gone without, she said.
Another, Victoria Robinson, said no water had been delivered to the elderly.