The U.S. Naval Academy has seized about 100 student computers that are suspected of containing unauthorized copies of copyrighted works.

The students were in class on Thursday when the raid occurred, according to an academy representative, who would not elaborate on other details of the investigation.

Each student gets a computer when they enter the academy. Illegal possession of copyrighted material could carry punishment including court-martial or a loss of leave, according to academy policy.

The seizure comes just a few weeks after movie and music industry trade groups sent a letter to more than 2,000 university and college presidents across the country, including officials at the Naval Academy, requesting help in cracking down on unauthorized file swapping.

In the October letter, the Recording Industry Association of America, the Motion Picture Association of America (MPAA) and other industry groups warned university officials that some students were using school networks to illegally trade copyrighted materials.

"Students must know that if they pirate copyrighted works they are subject to legal liability," the trade groups wrote. "It is no different from walking into the campus bookstore and in a clandestine manner walking out with a textbook without paying for it."

Colleges have become a hotbed for file-trading in recent years, partly because so many offer speedy Internet connections and partly because students tend to be avid music fans.

As a result, the entertainment industry has issued several warnings to universities. Last year, the MPAA and smaller copyright holders sent cease-and-desist letters to schools warning them about violations using school networks. In Napster's heyday, several colleges were the target of lawsuits brought by Metallica and Dr. Dre, who claimed the schools allowed people to trade unauthorized copies of their music illegally.

Universities have dealt with the warnings in a wide variety of ways. Some have taken a hands-off approach to student activities. Others have adopted bandwidth management tools to block or restrict file swapping.