Police in Shanghai are investigating the first fake Expo 2010 Shanghai ticket discovered on Wednesday, causing Expo organizers to remind the public to purchase tickets only from authorized dealers.

According to the Bureau of Shanghai World Expo Coordination, the first bogus Expo ticket was found on May 26, while the practice of collecting used tickets and reselling them has been reported since the fair's opening on May 1.

The police have vowed to combat the counterfeiting. Meanwhile, the public is advised to get their tickets from authorized dealers including designated agencies, selected tourism agencies and on-site box offices at the Expo Garden.

The public can identify the fake passes from feeling the surface and comparing the colors on the bottom edges.

Visitors could also get help from inspection machines at certain selling points if they question the authenticity of their tickets.

Also, group tickets are sold only via designated tourism agencies and can only be used at Expo entrances for group visitors.

Organizers also alerted the public that buyers should be careful about peddlers who try to resell used tickets, which always have a press mark of EXPO2010 or have been hole-punched.