SIOUX FALLS, S.D. — A longtime critic of a U.S. immigration program that attracts foreign investment in exchange for green card qualifications says it tends to draw marginal business opportunities that would have trouble securing regular financing.

Construction of the idled Northern Beef Packers plant in South Dakota was spurred by funds from the EB-5 program, in which foreign investors can secure permanent residency for as little as $500,000. Former plant officials say federal investigators have been asking questions about the financial dealings and EB-5.