The casino company owned by American billionaire Sheldon Adelson, a close ally of Prime Minister Benjamin Netanyahu, has been under federal investigation for the last year for alleged bribery of foreign officials, ABC News reported over the weekend.

Adelson, the main donor to U.S. presidential candidate Newt Gingrich and the owner of the Israeli daily Israel Hayom, holds 49% of the Sands casino company, and according to reports, is directly involved in the company's operations. The casino that the company set up in the Chinese island of Macau turned it into the largest gambling company in the world.

Open gallery view Sheldon Adelson Credit: AP

Last year, the Department of Justice and the Securities Exchange Commission launched an investigation into Adelson's alleged bribery of Chinese officials.

According to ABC, Sands casinos was allegedly cooperating with Chinese organized crime groups, known as triads, who allegedly organized high stakes gambling and sex junkets.

Chinese press reported at the time that more than 100 prostitues were found in the casino, during a raid by local authorities. A former manager at the casino, Steven C. Jacobs, sued Sands, claiming that Adelson told him to remain silent regarding investigation taking place against the company.

Adelson reportedly instructed Jacobs to refrain from reporting to the corporate board of Sands about the company's ties to the local crime organizations. Jacobs also claimed that Adelson wanted to investigate high-ranking officials in Macau to provide him "leverage" over any attempts to hurt the company.

Last year, Adelson commented on Jacobs' lawsuit and said that it is merely an attempt at blackmail and that Jacobs is trying to take revenge upon the country using a lies after he was fired.

Several months ago, Adelson contributed $5 million to Winning Our Future, a pro-Gingrich super PAC. More recently, Adelson's wife gave another $5 million to the same super PAC, providing a major lift to the former House Speaker's campaign.