Four people have been detained on suspicion of involving in a sex video tape at a Uniqlo store in Beijing, local police said Sunday.

Three people have been put under administrative detention on suspicion of spreading pornographic information and a 19-year-old man surnamed Sun is under criminal detention for spreading pornographic articles, Beijing police said on its official Weibo.

An employee in charge of Uniqlo stores in northern China told the Global Times Sunday on condition of anonymity that no Uniqlo employees are under investigation, and reiterated that the video was not a marketing gimmick.

The announcement came after the sex video, showing a young couple having sex in a fitting room of Sanlitun Uniqlo in Beijing, went viral on July 15.

In the video, the man, wearing glasses, a black T-shirt and jeans, is heard telling the naked woman to kiss him while using his iPhone to record the incident in front of the fitting room's mirror.

According to the police, the video was shot in the middle of April and leaked onto the Internet when it was sent to some friends via WeChat, while Sun uploaded the video on Sina Weibo.

The couple in the video were also called in by the police for interrogation, reported the Beijing-based newspaper Legal Mirror.

The woman was identified to be an undergraduate student while the man had a job, the newspaper added.

On July 15, the Cyberspace Administration of China ordered senior managers of top websites Sina and Tencent to fulfill their responsibilities and cooperate in the investigation on the sex video.