An unspecified number of sites were shut down by Immigration and Customs Enforcement agents that allegedly made unauthorized copies of movies and music available to visitors.
"ICE office of Homeland Security Investigations executed court-ordered seizure warrants against a number of domain names," ICE said in a written statement. "As this is an ongoing investigation, there are no additional details available at this time."
The New York Times said Saturday that affected sites were largely involved with the BitTorrent file-sharing system and may have numbered more than 70 sites. The Times said BitTorrent has been a difficult nut for prosecutors and the entertainment industry to crack because it operates on a widely decentralized basis.
The newspaper said BitTorrent users Friday were already passing the word on the Internet about new sites that were being created.