Federal prosecutors have issued a formal request to interview Prince Andrew as part of the government’s continuing investigation into accused child sex trafficker Jeffrey Epstein, a person familiar with the matter said.

The government’s action comes after prosecutors claimed that the the embattled Duke of York had failed to respond to earlier Justice Department inquiries.

Buckingham Palace did not immediately respond to inquiries. Great Britain’s Home Office declined to comment.

“As a matter of long-standing policy and practice, we neither confirm nor deny the existence of mutual legal assistance requests,” a Home Office spokesperson said Monday.

U.S. Attorney Geoffrey Berman, the chief federal prosecutor in Manhattan, said in January that Andrew had provided “zero” cooperation and that authorities were exploring other options.

Facing allegations that Epstein once forced a 17-year-old girl to have sex with the prince, Andrew announced in November that he was stepping away from his public duties as a royal. The prince and Buckingham Palace have cast the allegations as “false and without any foundation.”

In a statement announcing the change in his public role, the prince said he continued to “unequivocally regret my ill-judged association with Jeffrey Epstein.”

“I am willing to help any appropriate law enforcement agency with their investigations, if required.”

Federal authorities are continuing their investigation into the disgraced financier despite Epstein’s suicide in August in a Manhattan detention center, where he was awaiting trial on sex trafficking charges 

Andrew’s accuser, Virginia Roberts Giuffre, 36, has asserted that she was forced by Espstein to have sex with  Andrew three times when she was a teen. On those occasions, Giuffre said, she met the prince in New York, the U.S. Virgin Islands and in London.

In an interview with the BBC last year, the prince said he had “no recollection of ever meeting this lady, none whatsoever.”

Lawyers representing some of Epstein’s other accusers have issued statements urging him to fully cooperate with American investigators as they look into Epstein’s alleged trafficking network and his possible associates.