Police at an airport in Guangdong Province's Shenzhen City have detained five passengers whose "suspicious remarks" forced a flight to return to its departure city just 30 minutes after the plane's takeoff on Sunday.

The ZH9973 flight took off from Shenzhen Bao'an International Airport around 3:44pm and was bound for Chengdu, capital city of Sichuan Province, the Southern Metropolis Daily reported yesterday.

However, the plane returned to Shenzhen Bao'an International Airport around 5pm after attendants reported that they overheard some passengers talking "suspiciously," the report said.

The passengers, whose background remains unclear, were said to have talked to each other in a language that other passengers could not understand, which made them conspicuous.

One of them was said to have smiled to an air hostess and said she was very pretty.

The person then told the hostess that "she should watch the news tomorrow," which alerted the flight crew, the report said.

The plane returned to Shenzhen, where police detained the five passengers pending an investigation, the report said.

The flight took off again for Chengdu around 6pm on Sunday.

Shenzhen Airlines Co said the return was due to "flight security concerns," while the airport police declined to offer details as the case was under investigation.

The antiterrorism authority in Shenzhen may intervene in the case since "it has many suspicious points," the report said.

China foiled an attack on a flight to Beijing from Urumqi, capital city of Xinjiang Autonomous Region, on March 7.

The plane made an emergency landing after two suspected terrorists, including a 19-year-old woman, planned to ignite gasoline that they had smuggled onboard the China Southern Airlines flight.

The foiled attack, which was intended to disrupt plans for the Beijing Olympics, prompted China's aviation authority to ban passengers from taking liquids onto domestic flights.

Chinese police have broken up two terrorist rings plotting to sabotage the Beijing Olympic Games, Wu Heping, spokesman for the Ministry of Public Security said last week.

(Shanghai Daily April 15, 2008)