(ShareCast News) - United Utilities said on Friday that it is continuing to advise customers in Lancashire to boil their water before use after a routine test at Franklaw water treatment works in Preston found small traces of a microscopic bug in the water.Customers in Blackpool, Chorley, Fylde, Preston, South Ribble and Wyre are being urged to boil any water for drinking, food preparation and brushing teeth.United The company said the notice will remain in place throughout the weekend and into early next week at least."Samples of water from the treatment works and the wider network show that the traces of cryptosporidium are continuing to reduce. However, testing will continue and the boiled water notice will not be lifted until United Utilities is absolutely satisfied that the water is back to the usual extremely high standards," United Utilities said.It said investigations are ongoing as to how the bug found its way into the water at the treatment works.The company put out a public information notice on Thursday urging customers to boil drinking water until further notice.