SIOUX FALLS, S.D. — State officials began upping their oversight of a private company contracted to solicit foreign investors in 2012, but questions were first raised about South Dakota’s use of the federal investment-for-green-cards immigration program four years earlier.

The Government Operations and Audit Committee in 2008 wanted information about a little-known nonprofit at Northern State University called the South Dakota International Business Institute and its director, Joop Bollen.