Swedish police raided Web host PRQ earlier this week but it wasn't clear what they were after. Now, the ISP's owner is saying that the authorities seized servers for Web sites that allegedly dealt in illegal file-sharing.

According to TorrentFreak, police took three servers -- one belonged to one of Sweden's popular torrent sites called Tankafetast, another to an alleged Android app piracy site called Appbucket. It's unclear what was on the third server.

On Monday, the authorities targeted PRQ, which is known for hosting some of the most popular outlaw sites on the Internet. Former clients include the Pirate Bay and Wikileaks.

The Web host was also raided twice before, once in 2006 and another time in 2010. Both previous raids also had to do with investigations into alleged illegal file-sharing. PRQ is known for having a "don't ask, don't tell" policy when it comes to hosting sites that are unpopular with the authorities.

Swedish authorities still aren't saying why they raided PRQ this time and exactly what they were after.

According to TorrentFreak, Tankafetast decided to shutter itself in February but the site stayed online until the server was seized this week.

Appbucket hasn't been online since August, when its domain was seized by the U.S. Department of Justice in a sting that focused on pirated mobile apps. At the time, the feds announced that the servers hosting it were based overseas and they were calling on international law-enforcement partners for help.

This isn't the first time Swedish authorities have gone after an ISP this year. In March, the police requested that the hosting site Binero, where the Pirate Bay was registered at the time, divulge the personal details of whoever registered the site's domain name. Binero refused to comply with the request unless a proper warrant was served.