Ordinary residents will be invited to participate in the five trial operations in April for the World Expo, a senior organizer said yesterday.

The majority of participants in the citywide drills from April 20 to 25 will involve Expo site construction workers, staff in charge of exhibit arrangement and representatives from Shanghai and other parts of the Yangtze River Delta region.

The message came as Hong Hao, director of the Bureau of Shanghai World Expo Coordination, answered Internet users' questions in Beijing as a deputy to the National People's Congress (NPC), which will start its annual session tomorrow.

The China Pavilion, Theme Pavilion, Culture Center and Expo Center will open to visitors during the trials as well as some overseas pavilions.The aim is to test transport and security systems. Participants in each trial will range between 50,000 and 500,000.

The 2010 World Expo is estimated to welcome 70 million visitors.