Affluent foreigners are rushing to take advantage of a federal immigration program that offers them the chance to obtain a green card in return for investing in construction projects in the United States. With credit tight, the program has unexpectedly turned into a mainstay for the financing of these projects in New York, California, Texas and other states.

The number of foreign applicants, each of whom must invest at least $500,000 in a project, has nearly quadrupled in the last two years, to more than 3,800 in the 2011 fiscal year, officials said. Demand has grown so fast that the Obama administration, which is championing the program, is seeking to streamline the application process.

Still, some critics of the program have described it as an improper use of the immigration system to spur economic development — a cash-for-visas scheme. And an examination of the program by The New York Times suggests that in New York, developers and state officials are stretching the rules to qualify projects for this foreign financing.

These developers are often relying on gerrymandering techniques to create development zones that are supposedly in areas of high unemployment — and thus eligible for special concessions — but actually are in prosperous ones, according to federal and state records.