Beijing Railway Police declared security level upgrade on July 21, 2008 for the safety of Olympics. Anything entering the railway stations will subject to various security checks. Liquid will have to go through the “machine” from the date announced. Special police equipped with rifles are patrolling in all the four railway stations in Beijing. Detecting dogs are randomly checking goods round the clock.
Source: Xinhua, July 21, 2008
http://news.xinhuanet.com/olympics/2008-07/22/content_8742800.htm