Federal investigators say UCLA Medical Center staffers did nothing wrong when they performed liver transplants on four Japanese patients suspected of having ties to organized crime.

The surgeries were performed between 2000 and 2004, and drew ire because two of the patients donated $100,000 each to the hospital afterward.

UCLA officials have said they were unaware of the men's suspected ties to Japanese gangs known as yakuza.

According to a Centers for Medicare and Medicaid Services report reviewed by the Los Angeles Times, the livers offered to the Japanese patients had been turned down by other candidates over concerns about their size and quality.