The recording industry is suing four college students for allegedly offering more than one million copies of popular music over the Internet.

The Recording Industry Association of America (RIAA) has filed lawsuits in federal courts in New York, New Jersey and Michigan asking that the sites be shut down. The suits ask for damages of $150,000 per song.

"These systems are...illegal and operate in the same manner," said RIAA president Cary Sherman.

The entertainment industry launched a campaign last year against music downloaders, calling it a crime.

Famous singers from Eminem to Britney Spears and Pavarotti have appeared in print, radio and TV ads. A few years ago, the industry took file-swapping site Napster to court and won. The site was closed.

The music sector blames file-sharing networks for a downward trend in CD sales. The Digital Media Association (DMA), a lobby group representing file-sharing music sites, says file-sharing services help music sales.

The universities connected to the lawsuits say they will investigate the claims. All the schools have policies forbidding the use of their computer networks for copyright infringement.

Curtis Tompkins, the president of Michigan Technological University, says he wished the industry had contacted him before the lawsuits were filed. They had done so before when infringements were discovered.

"We would have shut off the student and not allowed the problem to grow to the size and scope that it is today," Tompkins said in a letter to the RIAA.

Matthew Oppenheim of the RIAA says this case was different and much bigger than previous ones. The student ran a network offering more than 650,000 music files for downloading.