ata belonging to 5,698 companies, including information used for their websites, has disappeared since a system failure last week knocked out a rental server service operated by a Yahoo Japan Corp. subsidiary, the company said today.

"Regrettably, we have determined that we cannot retrieve the data," Firstserver Inc. said on its website.

The Osaka-based company also said it is unable to rebuild the system, while it plans to compensate for the damages.

The system failure occurred around 5 PM Wednesday when the company tried to upgrade the server system's security, it said.

Firstserver has attributed the glitch to problems with its computer programming and operational procedures.

The company has also lost the backup data. The Ministry of Internal Affairs and Communications said it is investigating the details of the trouble, including whether or not the lost data contains private information.

Firstserver became a subsidiary of Yahoo Japan in November 2004 and provides a rental server service for more than 50,000 customers.

Kobayashi Pharmaceutical Co., one of the customers, said it spent two days retrieving the data by using its own backup files after most of its product lineup page and mobile phone-based site became unavailable Wednesday.