Tap water has been declared safe to drink in parts of Lancashire after a parasitic outbreak forced residents to boil their water for several weeks.
United Utilities said it has lifted the restriction for homes in parts of Blackpool, Chorley and Preston.
Hundreds of thousands of homes had been left having to boil their water after tests at one of the company's treatment plants uncovered traces of the microscopic cryptosporidium bug, which can cause sickness and diarrhoea.
The company said it has been "working around the clock" and its effort to eradicate the dangerous bug "is proving successful".
But the restriction remains in place for many homes across the county.
In a statement the company warned that removing the cryptosporidium bug from a water network covering 2,500 miles of pipework "is a complex process", but tests have shown that water quality is back to normal across some parts.
It added: "We always said that we would lift the boil water notice as soon as we were able to in those areas where there was no longer a risk to public health.
"We will continue our work to remove the bug from all parts of the Lancashire network and will lift the boil water notice in further areas as and when we are able to do so."
The company said it would write to customers once their water is safe to drink.
The firm added: "We all want things back to normal as quickly as possible and we're continuing to liaise closely with the Drinking Water Inspectorate and Public Health England, and meeting with them regularly to review the very latest test results.
"We're confident that the work we are doing is helping water quality to return to normal as quickly as possible.
"We will be compensating all homes and businesses who have been affected by the boil water advice notice."