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   Unlike previous take- down orders, this one was accompanied by no explanation from the authorities, the employees said.