BEIJING — Chinese regulators have ordered streaming video websites nationwide to take down four popular American TV series, a move that precedes new regulations seeking to close a loophole that has allowed foreign shows to flourish online, even as censors have limited them on broadcast television.

Censors with the State Administration of Press, Publication, Radio, Film and Television issued orders for video sites to stop showing “The Big Bang Theory,” “The Good Wife,” “NCIS” and “The Practice,” employees of two online streaming sites said Sunday. According to one employee, the order was issued Friday. Unlike previous take- down orders, this one was accompanied by no explanation from the authorities, the employees said.

After years of allowing foreign TV shows to rack up millions of views on Chinese streaming video websites, skirting the strict quotas and censorship enforced on broadcast networks, the government has indicated in private talks with Internet companies that it plans to close this control gap with new rules this year, company employees say.

In recent years, American shows like AMC’s “The Walking Dead,” the CW’s “The Vampire Diaries” and Netflix’s “House of Cards” have found avid online audiences in China, particularly among the growing middle class. With plenty of violence, superstition and scandal — all themes Chinese government censors frown upon — these shows would most likely never have made it onto Chinese television. But through the Internet, where censorship of online videos is looser than on TV, they have gained millions of fans through video websites that legally license the shows. And the government has taken note.