A policeman checks two passengers luggage at a metro station in Shanghai on Saturday, May 10, 2008. All Shanghai urban metro stops opened special security checkpoints on this day, through which commuters with luggage must pass one by one. Since April 15th, Shanghai has found more than 1,200 dangerous items, including gas cylinders and fireworks on its urban metro line and more than 700 passengers have been fined for taking the forbidden items on board. [Photo:cnsphoto]

On Saturday, all of Shanghais urban metro stops opened special security checkpoints.

Commuters with luggage must pass through the security corridor one by one, China News Service reports.

Shanghai has 9 metro lines with 161 stops, and on April 30th Shanghais urban metro transported a record 3.82 million passengers.

The boom in passengers has sparked security concerns, so in response, the Shanghai police have stationed more policemen and sniff dogs at the metro stops to carry out spot checks of commuters carrying bags or luggage.

The police also warned residents not to take any forbidden items on board, including paint, gasoline or fireworks to ensure the public safety.

On Friday, the city of Beijing also began tightening security checks on liquid beverages carried by metro passengers.

According to new security regulations, when checking in at metro stations passengers must drink from any bottles being carried to prove that they are not dangerous substances.

A bus fire that occurred in Shanghai on May 5th killing three people and injuring 12 others was caused by flammable goods, said the police.