South Dakota's Senate candidates, from left: Republican Mike Rounds; independent Larry Pressler; Democrat Rick Weiland, and independent Gordon Howie. (AP Photo/File)

The FBI is still "actively" probing South Dakota's EB-5 program, it was reported Wednesday -- a new detail that could further complicate the Senate campaign of former governor Mike Rounds (R).

The investigation "is active but I can't say anything more about it," FBI Minneapolis Division Chief Counsel Kyle Loven told The Washington Post Wednesday in a brief interview. He said the probe is focused on the South Dakota Regional Center.

According to its Web site, the center "manages limited partnerships which fund economic development projects on behalf of EB-5 investors in accordance with federal laws and regulations."

As the Sioux Falls Argus Leader reported, federal officials had previously refused to confirm or deny that the investigation was ongoing.

EB-5 is a federal program that allows immigrants to earn green cards by investing in U.S. job creating-enterprises. When Rounds was governor, the state officials in charge of the program there ran a problem-plagued operation. One of them, who authorities determined died by suicide last year, was facing an arrest at the time of his death for allegedly funneling state money to himself.

Democrats have dubbed the whole thing Rounds’s “Citizenship for sale scheme.” Rounds insists he did nothing wrong. The program is now closed in South Dakota.

Rounds faces a competitive three-way race that Republicans view as a must-have in the battle for the Senate majority. Long-favored to defeat Democrat Rick Weiland and independent Larry Pressler, recent polls show the race has tightened. National Democrats and Republicans have flooded the state with money in recent weeks.

Long-shot independent Gordon Howie is also running.

A campaign spokesman for Rounds did not immediately respond to a request for comment on the FBI investigation.