Chinanews, Beijing, July 27 - On July 25, Beijing police launched a campaign to check Olympic stadiums, gyms and other buildings for hidden security crises.Liu Honggang, an anti-riot policeman of Beijing Special Police Squad, was responsible of checking all the central heating systems in the National Conference Center, located to the north of the Water Cube natatorium. The fencing and 5-m pistol shooting events of the 2008 Beijing Olympic Games will be held here.The police took various detectors with them, ranging from explosive detectors to speculums for checking the interior of walls."There will be a similar check shortly before the opening of the ]Games," said Ma Hui, the leader of the anti-riot squad.The check will last till the construction of all the stadiums and gyms is completed. The project can be divided into three phases. The first phase will come to an end before September, and it will be the most important of the three, as the rest two designed only to check some trivial things.