U.S. officials are investigating the involvement of UN officials in a bribery scheme linked to real estate developments in Macau, China. Pictured: Signs for pawn shops are seen in Macau on Aug. 29, 2015. Reuters/Tyrone Siu

U.S. federal authorities are investigating a scheme in which officials at the United Nations (U.N.) were allegedly bribed for their support to develop real estate in Macau, the Wall Street Journal reported Tuesday, citing sources. The investigation follows the arrests of a Macau real-estate mogul and his assistant, who are both said to be connected to the scheme.

The report said that additional charges may be announced later Tuesday against several people involved in the scheme, including some U.N. officials still in office. The U.N. officials were not yet identified and more details about how the scheme worked were also not revealed. However, the Journal report added that some of the bribes were believed to have been sent to officials from the Caribbean. The investigation was conducted by U.S. Attorney for the Southern District of New York Preet Bharara’s office and the Federal Bureau of Investigation.

Ng Lap Seng, also known as David Ng, and his assistant Jeff C. Yin were arrested last month and charged with one count of conspiracy for lying to the U.S. customs about the $4.5 million in cash that they brought to the U.S. since 2013, the Journal reported. They were also alleged to have met an unidentified businessman in 2014 with $400,000 in a briefcase.

Ng is the chairman of Sun Kian Ip Group and a member of a top advisory body for the Chinese government. He has also held significant political positions in the Chinese territory of Macau, which is considered the world’s largest gambling hub, the report said.

Ng has worked, individually and through Sun Kian, with the United Nations Office for South-South Cooperation, which helps build economic and political partnerships among developing nations. He is alleged to have wired over $19 million since 2010 to individuals and entities in the U.S. Ng and Yin are currently being held in New York by officials, who count them as flight risks.

Alex Spiro, one of the lawyers for Ng, said Monday, according to the Journal, that he had “committed no crime” while Kevin Tung, another lawyer for Ng, said that he was innocent.

Sabrina Shroff, a public defender representing Yin, said, according to the Journal, that her client was just “an employee and nothing more of the main defendant.”

Sun Kian, which has its foundations in New York City and Macau, describes itself as seeking to serve “as a facilitator for key stakeholders in building the capacity of developing countries,” mainly for the southern hemisphere. The company also reportedly publicizes several current and former U.N. officials in its leadership while several other documents and domains allegedly showed links with other organizations working in developing countries and the U.N.