Lancashire water: Cryptosporidium 'still present' in supply
More than 300,000 households in Lancashire have been warned they may have to boil drinking water until at least Wednesday.
"Low levels" of a microbial parasite remain in the supply, United Utilities said.
There was one clear test overnight, but further tests are required before the boil notice can be lifted, the firm said.
Samples are said to have "improved" but not returned to normal.
The alert affects Blackpool, Chorley, Fylde, Preston, South Ribble, Wyre and the Mellor area of Blackburn.
Investigations continue into how traces of cryptosporidium, which can cause stomach upsets, got into Franklaw water treatment works outside Preston.
Over the weekend, leaflets were distributed to many of the affected homes and businesses offering advice.
'Clear samples needed'
Jo Harrison, from United Utilities, said: "Our teams are continuing to investigate the problems, it's very complex as you can image.
"We are hoping that we will get some better news by the middle of the week but we need to make sure the system is absolutely safe before we allow people to drink the water again.
"We want to make sure that we get a complete series of clear samples for a good period of time before we change our advice."
Compensation for affected businesses will be considered after the water issue has been resolved, the water company said.
Cryptosporidium exists in the environment in a form called an oocyst, which is less than a tenth of the thickness of a human hair.
Infection with the parasite can cause diarrhoea and abdominal cramps.
People with weak immune systems are likely to be more seriously affected.
Kate Brierley, deputy director for Public Health England in Cumbria and Lancashire, said: "We are recommending people to boil the water before they drink it or brush their teeth.
"Most people would just get a mild tummy upset which might last for a few days or a little bit longer.
"If somebody's immune system is upset for some reason - either because they have an illness or because of treatment like chemotherapy - they are more vulnerable than the general public."
Several supermarkets in the county have increased deliveries of bottled water to avoid running low.
Water advice includes
- Use tap water for general domestic purposes such as bathing, flushing toilets or washing clothes
- All water for drinking, food preparation and brushing teeth should be boiled as a precaution
- It is safe to eat food after washing your hands
- Using boiled water for washing dishes is the best practice
- Dishwashers are safe as long the setting is at 65 degrees or above
Source: United Utilities
What is cryptosporidium?
- A microscopic parasite which lives in, or on, other organisms
- Found in soil, water or food contaminated with animal or human faeces
- Infection occurs via contact with infected animals in farms or zoos or by drinking contaminated water
- One of the most common causes of diarrhoea in humans
- It most commonly affects children under five but people with impaired immune systems are at risk