The lack of copyright and violating regulations are the two reasons for the recent removal of several popular American TV series from Chinese video streaming sites, according to China's broadcast watchdog.

In a reply to an information disclosure request from students from Wuhan University, Hubei Province, the State Administration of Press, Publication, Radio, Film and Television said on Friday that some of those banned shows are out of copyright and the other contained information which violated Clause 16 of a regulation over online broadcasting programs.

Clause 16 stipulates that programs aired online should not have content that violates China's constitution, endangers the country's sovereignty and territorial integrity, provokes troubles in society, promotes illegal religion and triggers ethnic hatred. Pornographic and violent content is also banned.

The Center for Protection for the Rights of Disadvantaged Citizens of Wuhan University posted the reply on its Sina Weibo account. The request was sent in April.

Popular shows The Big Bang Theory, The Good Wife, NCIS and The Practice were no longer available on tv.sohu.com, youku.com, and v.qq.com since April 26. The shows were all purchased legally for viewing in China, said the websites.

American and British TV dramas are becoming increasingly popular in China with video streaming sites stepping up their imports. In 2011, the cost for importing The Big Bang Theory was $150,000 per episode, proving that importing shows has become big business.

In March, the State Administration of Press, Publication, Radio, Film and Television issued a notice on reinforcing content examination over online audio and visual programs.

According to the latest notice from the administration, TV series broadcast on television from July to October should be in line with the "Chinese Dream." The content of the shows should be realistic and focus on indicating patriotism and family love.