About 31,000 people have been told to boil their water following a fault at the treatment works at Broken Scar on Tuesday.

The notice is still in place – but tests on samples have so far come back clear, Northumbrian Water said.

Last night, the company handed out bottled water to about 300 vulnerable customers.

Read more: Northumbrian Water response to Darlington fault 'shambolic'

And about 20,000 bottles of water have also been delivered to 60 schools and 25 nurseries within the impacted area.

Northumbrian Water’s Water Director Keith Haslett said: “We’re cautiously optimistic about the results received back so far from our initial tests.

LIVE: Darlington residents told to boil water amid Northumbrian Water issue

“They’re coming back clear and if this continues and all of the other test results come back the same, then we’re hopeful of being able to lift the restriction. Until then it’s really important that customers in the areas of Darlington where the boil notice is in place keep boiling any drinking water.

“Although the risk to the water causing people any harm is very low, there is still a risk and that’s why we felt it was important to issue the precautionary warning that we did.

“We’re sorry for any issues that has caused our customers and we’re working around the clock to get it resolved.”

The problem was caused by a fault with a valve at Broken Scar treatment works, which allowed a small amount of water into the networks that had not been fully disinfected.

Northumbrian Water made the decision with UK Health Service Agency (formerly Public Health England) to advise people in some postcodes in Darlington to boil their water as a precaution.

Read more: Northumbrian Water issues: Full list of affected postcodes

The company came under fire at a Darlington Borough Council meeting last night, with members criticising the response as shambolic. 

Councillors criticised the reaction time of the firm to the  public health risk affecting 31,000 households, describing it as disappointing and gravely concerning.

Since the issue emerged, teams from the water company have been carrying out a full review of the water networks and doing sampling tests across Darlington and initial test samples have all come back clear so far, the company said.

Further test results are expected tomorrow which should give an indication of whether restrictions can be lifted on Thursday or Friday.

On Tuesday night hundreds of Northumbrian Water employees were on the ground delivering boil water notices to more than 15,000 properties and delivering bottled water to almost 300 priority services vulnerable customers.

15,500 text messages were sent to customers on the situation and regular updates are being posted on the Northumbrian Water social media channels. These updates will continue in the coming days.

Early on Wednesday morning, teams were deployed to school gates across the Darlington area with around 20,000 bottles of water for 60 schools and 25 nurseries within the impacted area.

The exact postcodes of the areas affected are:

DL1 1**, DL1 2**, DL1 3**, DL1 4**, DL1 5**, DL2 1**, DL2 2**, DL3 0**, DL3 6**, DL3 7**, DL3 8**, DL3 9**.

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