The van, which was not expected to give away bottled water but instead hand out information and advice, suffered mechanical problems on its way to the town centre.

The unit was expected in town early this morning, but only arrived after 3pm.

A spokesman for Anglian Water said: "The unit suffered mechanical problems and could not make it to the Market Square first thing in the morning."

As the crisis continued, a spokeswoman said staff had been working through the night to try to fix the cryptosporidium contamination in the water system, but said the advice was still for people to boil their water before drinking it.

She said: "We are giving water away to schools, nurseries, hospitals and to vulnerable people but other people can boil their water and let it cool down before they drink it.

"We want to apologise again to customers. We are doing everything we can."

She added specialist equipment was being taken to Pitsford, where the contamination occurred, to start a filtering programme tomorrow to try to get the bacteria out of the system.

Customers with a disability who would like to be added to the vulnerable list to receive bottled water, or anyone who needs information or advice on the situation can call 08457 145145 or log on to www.anglianwater.co.uk.