The European Union Rule of Law mission in Kosovo has appointed an American prosecutor to investigate allegations that Prime Minister Hashim Thaci and other senior figures were involved in an organ-trafficking network.

In a statement Monday, the mission, known as EULEX, said John Clint Williamson of the United States was named the lead prosecutor of the task force. The force is charged with investigating reports that former Kosovo rebels trafficked in human organs to raise funds for their fight for independence during the late 1990s.

A Council of Europe report last December alleged that Prime Minister Thaci once headed a criminal organization that profited from the organ trade. The report said there were “numerous indications” the former Kosovo Liberation Army ran detention centers along Albania's border with Kosovo, where captives, including Serbs, were killed and their organs sold on the black market.

Mr. Thaci has denied the allegations, calling the report a fabrication designed to malign Kosovo.

EULEX was established only months after Kosovo declared independence from Serbia to help Kosovo law enforcement agencies develop sustainability and accountability.