Chinese authorities have beefed up security checks at all airports in the northwestern Xinjiang Uygur Autonomous Region by deploying explosives detectors to foil possible terror attacks before and during the Beijing Olympics and Paralympics.

A total of 42 explosives trace detectors, or ETDs, were installed at all entrances to terminal buildings of the 13 airports in the region, said Zhong Conglin, head of the security check department with the Xinjiang Airport Group Co. Ltd.

In addition to the routine security check before boarding a plane, passengers must also receive ETD checks first before entering terminals, he said. "That is to prevent violent terrorists from bringing explosives to airports."

Zhong revealed that security staff found a bullet in the luggage of a passenger at the international airport in Urumqi, the regional capital. The passenger, who was heading for Bishkek, was detained by police and was now under investigation.

He would not provide further details about the case, such as the passenger's nationality.

In March, a China Southern Airlines crew foiled an attempted airline bombing on a Urumqi-Beijing flight. A 19-year-old female of Uygur ethnic background, Guzalinur Turdi, confessed to the failed terrorist attack. She and others involved in the case were apprehended by police.

ETDs are security equipment able to sniff out explosives of small magnitude or other chemicals. The equipment is used mainly in airports and other vulnerable areas considered susceptible to acts of unlawful interference.

The Civil Aviation Administration of China (CAAC) ordered enhanced security checks at all terminal entrances in a number of cities to guarantee a safe Olympics and Paralympics.

Apart from the Beijing Capital International Airport (BCIA) and those in Xinjiang and Tibet Autonomous Region, the list includes others in five Olympic co-host cities on the Chinese mainland -- Shanghai, Qingdao, Tianjin, Shenyang and Qinhuangdao. Also included were Shijiazhuang, Taiyuan and Nanjing.

The move was the CAAC's latest to better protect flight safety. Previously it banned liquids, lighters and matches from carry-on luggage and required passengers to remove their shoes for safety checks.

Photograph: A security officer checks a passenger's bag at Urumqi International Airport in Xinjiang Uygur Autonomous Region on July 22, 2008.