Scrap metal thieves blamed for knocking out websites including Sainsbury's

The grocery ordering service of the UK's third biggest supermarket went off line in the early hours and did not return until around 3pm.

It is the third time in a matter of weeks that the service has been shut down. The failures that have prevented thousands of orders with an estimated value of more than £2million.

Off line: Sainsbury's website was unavailable for a time today after a computer failure that is being blamed on scrap metal thieves

The latest problem was traced to a break-in and theft from a computer network centre owned and run by telecoms company Cable & Wireless in Watford.

The theft of key equipment knocked out the Sainsbury's website and others run by the Ordnance Survey and the FT.

One theory is that thieves looking for copper wire, which has a high scrap value, may have been behind the break-in and theft of equipment and cables.

Earlier this week, police forces around the country highlighted that the thefts of metal, including lead from church roofs, is the fastest growing crime in the country.

Sainsbury's first lost its website for two days in the middle of June due to technical problems.

It went down for a short time last week following a power failure at one of its internet service providers.

The system failure today, normally a busy day for orders, was entirely due to the problems at the Watford site and had no connection to the earlier problems.

While the store could not take new orders for a time, the failure did not prevent it going ahead with deliveries that had previously been booked.

The technical problems are serious for Sainsbury's for it opens the door to rival services from Tesco, Asda and Ocado to grab custom.

During earlier problems, these rival firms have offered incentives to new customers, including money off vouchers and free delivery.

Sainsbury's said: 'As a result of a technical problem that, Cable & Wireless, our internet provider experienced, customers were unable to gain access to our groceries website on Thursday until early afternoon.

'No customer deliveries have been affected.'

Cable & Wireless said the problems followed a theft from a network site in Watford, Hertfordshire, overnight.

A spokesman said: 'We have experienced some network issues that have regrettably affected a number of our customers.

'The issues have arisen following a break-in at one of our network sites in Watford, in which some of our equipment was stolen. This has interrupted services to customers for whom we provide managed hosting services.

'We are in the process of investigating the incident and have deployed specialist engineers to work on restoring full services to affected customers as quickly as possible.

'Delivering a great service to customers is our core priority, and we are working with those affected to minimise the impact on their business.'