Warner Bros., 20th Century Fox and other big TV producers in the U.S. are suing Koreans who have created subtitles for popular American TV series that were distributed illegally on the Internet.

Police here are investigating 15 people.

This is the first time that individuals here have been sued for merely making the subtitles for pirated TV series.

People who make subtitles without permission from the original authors or producers could face a jail sentence.

The suits allege that the subtitles created by the 15 Koreans enabled millions of viewers here to watch the shows even though they do not understand English.

The lawsuits have prompted illegal streaming websites here to shut down voluntarily.

American TV series have enjoyed a huge worldwide renaissance in the last decade that has not spared Korea, where the show "Prison Break" became subject to a near-cult in 2005.

According to a survey conducted by one network, around 40 percent of Korean adults have been exposed to American TV dramas through various channels. One of the biggest domestic websites streaming U.S. series has more than 200,000 members, some of whom volunta rily create subtitles and upload them.

HBO's fantasy hit "Game of Thrones" ranked No. 1 among the most downloaded programs on the file-sharing website BitTorrent last year, which is immensely popular among Koreans. The drama, based on George R.R. Martin's series of doorstoppers, racked up a total of 5.9 million downloads around the world last year.