Web hosting provider 123-reg has accidentally deleted data from an unknown number of its virtual private servers (VPS), where customers' websites were hosted.

The company—which has around 800,000 customers in the UK—has been trying to restore the data since Saturday morning, however some websites remain offline more than two days since the incident occurred.

In an e-mail to irate customers, 123-reg admitted that the data was removed by a clean-up script.

This script is run to show us the number of machines active against the master database. An error on the script showed 'zero-records' response from the database for some live VPS. For those customers, this created a 'failure' scenario...effectively deleting what was on the host. As a result of our team's investigations, we can conclude that the issues faced having resulted in some data loss for some customers.

Ars sought comment from 123-reg—which is responsible for 1.7 million websites in the UK, although not all of them are hosted on VPS—but it hadn't got back to us at time of publication. The firm told the BBC that only a "small proportion" of websites had been deleted by the script.

The company has been providing regular updates about the blunder on the status page of its website. 123-reg has also advised website owners to—where possible—use local backups instead of waiting for its sysadmins to finish the job.

"Due to the nature of this process, we are unable to prioritise the recovery of specific hosts, but we are focused on restoring bulks of data at the moment," 123-reg said in an update on Monday morning. "Progress is visible, and we have already managed restoring a certain number of hosts. However, we are unable to estimate when will the recovery be finished on all of the affected packages."

Meanwhile, frustrated customers have vented their anger on Twitter. The website owner of Outlines Design said: "Spoke with @123reg earlier today regarding VPS issues. Was told a week minimum for email update and more than likely all data lost."

Ars will update this story if 123-reg reveals more about what went wrong.

Update

123-reg provided Ars with the following statement an hour after this story was published:

We suffered a technical fault, which has affected a minority of 123 Reg customers. The fault was limited to 67 servers out of 115,000 (across Europe) and it is important to note that only a selection of customers on the 67 servers affected has been impacted. We are investigating the restoration of each VPS on a case-by-case basis and are working individually with customers to keep them informed of the website recovery process. We are working as quickly as we can to restore service to normal. Our VPS product is an unmanaged service and we always recommend that customers implement backups to safeguard against unexpected issues. Customers who had purchased 123 Reg backups can be online now as can those who are using another solution for website backup. If customers restore from their own backups, this will not overwrite our efforts. Additionally, customers who have restored from their own backups are now hosted on new servers. By using new servers, we will ensure that we do not overwrite the previous servers and impact the data recovery process.

The company said that data recovery outfit Kroll was helping 123-reg with the "process of restoration."

123-reg added: "We would like to extend our apologies to affected customers and assure them that we are doing everything we can to restore their data as quickly as possible. We are keeping customers informed as we restore their websites."