Fire knocked out power at the Aruba Internet service provider's server farm on Friday, forcing tens of thousands of websites offline.

Aruba, one of Italy's largest Web hosting services, said the fire at its primary server farm in the central Italian town of Arezzo first knocked out its backup power source. Automatic fire safety systems, in turn, forced off the main power.

Aruba said in a service notice to clients posted on its website that the fire did not spread to servers or rooms where data are stored.

The fire hit about 4 am (local time), and took about 3 1/2 hours to put out, the news agency ANSA reported.

Restoring service took more time. Aruba posted a notice about 11 hours after the blaze started saying power had been restored in all the effected areas.

Websites were slowly coming back on line across the country, ANSA said, with sites for companies in Tuscany working by midday.

Aruba is one of Italy's largest Internet service providers, offering domain name registration, website hosting and dedicated servers. Its customer base is primarily small- and medium-size businesses.

Users flocked to Twitter to share their dissatisfaction, and some noted that competitors were using the incident to entice customers away from Aruba.

The Codacons consumer advocacy group, meanwhile, said it was studying the possibility of a class-action lawsuit, citing "enormous economic damage," to clients who didn't have access to email or whose websites were down.

The Aruba Group, which also operates in the Czech Republic and Slovakia, hosts 1.25 million websites, according to its own website.