A Chinese woman suspected of selling a banned drug online from a base in Thailand was brought back to Beijing on Tuesday, the municipal police said.

The 24-year-old, surnamed Huang, was arrested in Bangkok on Aug 8 in a joint operation by officers from the capital and Thailand, said the Beijing Municipal Public Security Bureau.

The bureau's economic investigation department started to examine the selling of diet pills named Yanhee on micro-blogging and instant messaging sites in July last year.

Checks by the capital's food and medicine watchdog showed the pills contained substances that were banned in China.

Police traced the pills and found they were being distributed from Thailand.

Officers had previously smashed 39 gangs suspected of selling the drug in the capital, seizing more than 10 million pills and detaining 22 people.

Beijing police decided to arrest Huang, a native of the Guangxi Zhuang autonomous region, last November, but could not do so because she was in Thailand.

However, following assistance from the Ministry of Public Security, they were able to work with officers in Bangkok to determine where she lived and detain her.