The lighting system of the World Expo axis is tested in Shanghai, east China, March 31, 2010. The Shanghai World Expo will start trial operation on April 20 with the participation of about 70 percent of the pavilions, the organizer said on March 31 Tuesday. (Xinhua Photo)

 With only 30 days left, Shanghai is busy ironing out kinks and making sure it is ready for the most extravagant Expo in 151 years.

The city is adding final touches to infrastructure and beautification projects and trying to ensure all Expo pavilions open on time.

At a press conference to announce the 30-day countdown to the start of Expo 2010, Shanghai's vice-mayor Yang Xiong denied earlier reports that up to 20 percent of pavilions will not be ready by May 1.

Yang said delays are common for Expos and less than 10 percent of projects will have a delayed start.

The delays are mostly caused by problems transporting pavilion exhibition materials and the complicated design of some structures.

While Expo organizers are predicting that 70 million people, mostly Chinese, will visit the event, a number of insiders told China Daily they believe the number will top 100 million.

Because of this, security is a huge concern, especially in the wake of this week's suicide bombings at metro stations in Moscow, which killed 39 people.

But organizers are confident they can keep a lid on such threats by imposing tight checks on entrances to Expo garden, Yang said. No liquids, sharp items, matches or lighters will be allowed into Expo.

X-ray scans of commuters' carry bags have been expanded to all metro stations in Shanghai.

Another concern for organizers is crowd control at Expo entrances, where an average of 400,000 people will be passing through daily.