Sainsbury's, the UK's second-biggest retailer, suspended its online shop on Tuesday because of a glitch in its ordering system.
A spokesman said no customer details were lost and customer details were not affected. She could not say what the cause of the glitch was, but said it was "internal" rather than "external".
In its interim report this morning Sainsbury's reported online sales in the first quarter grew more than 40% over the same period last year.
The news comes a week after Cotton Traders said that it had lost customer details after hackers corrupted its website. According to the BBC, more than 38,000 customers were affected, a number denied by Cotton Traders.
In a statement, Sainsbury's said, "We suspended our online home delivery website late yesterday afternoon when we identified a technical issue. By mid-morning we had already contacted the overall majority of customers who have been impacted to advise them to place their order again once we have resolved the problem.
"We have offered all affected customers a £10 e-voucher to spend online once normal service has been resumed. We are now starting to call customers who had placed orders for tomorrow as we are now unable to fulfil them and we are working hard to resume normal service as soon as possible and will communicate with customers as soon as this happens.
"Like many online retailers, from time to time we do have technical glitches and only want our customers to have access to a site that we are 100% happy with."