The number of people visiting the Shanghai Expo Exhibition Center on Huaihai Road M. hit more than 15,000 during the May Day holiday.

The center was also packed on Sunday, even though most people had returned to work after the three-day break.

The center received 11,500 people during the May Day holiday and on May 2, the number climbed to more than 5,000.

"Reservations for May 5, 6 and 7 are already full," Li Ruixia, operation director of the exhibition center, revealed Sunday, adding that the three reservation hotlines haven't stopped ringing for four days.

The organizers had set a ceiling limit of 3,000 visitors daily, but the enthusiasm of local residents was so high that they had to allow many more people on Friday.

One-day admission to the Expo is tentatively set at 160 yuan (US$22.9) for adults. Discounted admission for children, seniors and groups will be announced later.