CHENGDU, China—When the government of this southwestern city needed a landmark for a new district, billionaire developer Deng Hong picked up the land cheap five years ago and erected a building almost three times the size of the Pentagon. Nearby, Wu Bing paved a motorway, while Liu Han put up schools. He Yan wired a jail with information technology and Wang Junlin's winery funded government charities.

Now, over the past several months, all of those tycoons have disappeared from view. Their absences come amid an alleged corruption scandal that may broadside the economic vitality of this gateway to China's rugged west and indicate a fresh front in Chinese political infighting.