United Utilities urged residents to boil their drinking water after traces of the bug cryptosporidium – a microscopic parasite which can cause stomach cramps and diarrhoea - was found at Franklaw Water treatment plant in Catterall, near Garstang.
Supermarkets are now being cleared of bottled water following the find.
One staff member at Asda in Fulwood said he’d never seen the shelves so empty as customers rushed to fill up.
Shopper Lynda Garburr, 46, from in Catterall, had a trolley loaded to the brim with bottled water for the children at a holiday club she runs at Harris Primary School in Fulwood.
She said: “The children have to be safe, that is why we are buying all this water,
“I’ve noticed quite a few people unpacking loads of water from trolleys into cars outside.”
Leona Worth, 45, Fulwood, Preston, said: “I am very concerned I have two young children.
“I have only just heard about it on the news. I am panicking because I have been drinking water all day.
“I’ve never heard of this before. I’m a concerned parent.”
Carly Whittam, from Woodplumpton, said: “I have been off sick with a virus.
“I have been in bed all week. I’m concerned that this the water is what has caused it because I’ve been feeling worse again today. We won’t be letting the kids drink water.”
Low traces of the bug was discovered during routine tests at the water treatment plant and the water company is now running further tests.
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