Collecting Expo passport stamps from pavilions has become so popular that the passports are selling out soon after the gates open every morning at Expo Garden.

The 49-page passport is a way for visitors to collect commemorative stamps from each pavilion they visit.

Due to the shortage, visitors are coming up with creative ways to collect the stamps without using the 30-yuan passports.

Hou Peiqi and her family lined up at the Bangladesh Pavilion at the Asia Joint Pavilion waiting for her 25th stamp. With no Expo passport to put it in, she decided instead to have the stamp placed on a map of the Expo.

"I'd rather have them stamped in an Expo passport, but they have sold out in the souvenir stores. So I have to use this map," said Hou.

Hou is one of thousands of visitors to the Expo Garden who failed to get an Expo passport because of a short supply.

They are now one of the hottest items at the Expo Garden.

On Saturday, the opening day of the Expo, the 110,000 available Expo passports were sold out within a few hours, leaving more than 100,000 visitors disappointed.

"The most frequently asked question is 'where can I find an Expo passport?'" said Yang Haiyan, a receptionist at a souvenir store in the Expo Garden.

In the face of such a shortage, some Expo visitors have been creative, asking pavilion staff to stamp their maps, books, newspapers and even T-shirts.

"Every pavilion has unique features and it is a great chance for me to learn about different cultures. The stamps are a reminder of my trip," said Hou. "I want to collect as many stamps as I can."

For visitors from outside Shanghai, stamped Expo passports have become a popular gift for friends and relatives.

"I can share my happiness with my family," said Zhao Yueru from Henan province, who purchased 12 Expo passports.

Compared to the over-crowed European and Asian pavilions, stamp collectors prefer the joint pavilions. Most visitors can have their passports stamped in less than five minutes. But some pavilions have had trouble keeping up with the demand for stamps.

"Countless people approached me and asked me to put stamps in their passports, and the stamps have run out of ink several times," said Genevieve Leopold at the Seychelles Pavilion in the Africa Joint Pavilion.

Corporate and theme pavilions in the Puxi zones are also allowed to stamp passports for the first time in Expo history.

"We have prepared 10 stamps for visitors to choose from," said Hu Xiaofeng, spokesman of the China Shipbuilding Industry Corporation Pavilion.

Collecting commemorative stamps for Expo passports is an Expo tradition. The practice originated at the 1967 Expo in Montreal, when the passport served as a ticket.