King Charles III addressed his younger brother’s arrest, saying that "the law must take its course" in the investigation of former Prince Andrew.

"I have learned with the deepest concern the news about Andrew Mountbatten-Windsor and suspicion of misconduct in public office," he said in a statement.

King Charles went on to state that what follows is "the full, fair and proper process by which this issue is investigated in the appropriate manner and by the appropriate authorities."

"In this, as I have said before, they have our full and wholehearted support and co-operation," he continued.

"Let me state clearly: the law must take its course," King Charles said, adding, "As this process continues, it would not be right for me to comment further on this matter. Meanwhile, my family and I will continue in our duty and service to you all."

Andrew, who was stripped of his royal titles over his links to convicted sex offender Jeffrey Epstein, was arrested on Thursday — his 66th birthday — on suspicion of misconduct in public office.

While he has consistently denied any wrongdoing connected to his friendship with Epstein, scrutiny over their relationship has shadowed the royal family for more than a decade.

Earlier this month, Andrew moved to King Charles III’s estate in Norfolk after being evicted from his longtime home near Windsor Castle.

Thames Valley Police had previously said it was "assessing" allegations that he sent confidential trade reports to Epstein in 2010, when he served as Britain’s special envoy for international trade.

The claims stem from correspondence between the two men included in millions of pages of U.S. Justice Department documents released last month as part of the Epstein investigation.

"Following a thorough assessment, we have now opened an investigation into this allegation of misconduct in public office," Assistant Chief Constable Oliver Wright said. "We understand the significant public interest in this case, and we will provide updates at the appropriate time."

The Associated Press and Reuters contributed to this report.