What caused the deadly Shanghai stampede?

Thirty-five people died in a stampede during New Year's celebrations in downtown Shanghai, city officials said Thursday - the worst disaster to hit one of China's showcase cities in recent years. A Shanghai government statement said another 43 people were injured amid the chaos about a half-hour before midnight. Revellers were trampled to death after coupons printed to look like dollar bills were thrown from a nearby building. he official Xinhua News Agency quoted an unnamed witness as saying people had scrambled for coupons that looked like dollar bills that were being thrown out of a third-floor window. It said the cause of the stampede was still under investigation.