George Nader, a Lebanese-American businessman with deep ties to the United Arab Emirates who became a key witness in the Mueller investigation, was arrested Monday for allegedly possessing child pornography, authorities said.

The charges were unsealed Monday when Nader was arrested at New York’s John F. Kennedy International Airport.

Nader was charged in January 2018 after he arrived at Washington-Dulles International Airport from Dubai, according to the complaint. He allegedly transported “child pornography and child erotica,” including videos showing children as young as three years old, according to the complaint.

Judge Cheryl Pollak in New York ordered Nader to be detained overnight after Assistant United States Attorney Miriam Glaser sought his detention, arguing that he was a danger to the community and a flight risk, according to the U.S. Attorney's Office for the Eastern District of New York.

Pollak requested additional medical information pertaining for Nader and an additional suretor posting property on a bond. The bail hearing is set to resume tomorrow at 2 p.m.

Nader, 60, previously pleaded guilty to the same charge in 1991. His lawyers did not immediately respond to a request for comment.

When Nader landed in the U.S. last year, he was served with search warrants for his phones pertaining to a matter not involving child pornography, according to the complaint. FBI agents confiscated three different iPhones and interviewed him, the complaint said.

Nader’s precise work for the UAE is shrouded in mystery, but he has a long history of working with Democrats and Republicans and forged a relationship with the Trump campaign in 2016. That relationship strengthened as time went on and eventually Nader operated within Trump’s inner circle. He began cooperating with Special Counsel Robert Mueller’s office soon after he was stopped in 2018.

Investigators were particularly interested in two meetings.

Nader helped set up a meeting between Blackwater founder Erik Prince and Kirill Dmitriev, the head of one of Russia’s sovereign wealth funds, the Seychelles in January 2017. Dmitriev floated a “reconciliation plan” between the U.S. and Russia to Prince, an advisor to the Trump campaign. The Mueller Report said Prince received information about Dmitriev before he landed on the island—something Prince denied in front of Congress.

In August 2016 Nader met with several members of Trump’s team, including Prince, Donald Trump Jr., and Joel Zamel, the owner of Israeli-linked intelligence firm Wikistrat. Among other things, they discussed how to help Trump win the election in 2016, including a social media manipulation plan that would use fake accounts to promote Trump on Facebook and elsewhere. It’s unclear if that plan was ever carried out, though sources inside the West Wing deny that it was ever seriously considered.

Nader reportedly received partial immunity for agreeing to cooperate with the Justice Department and testifying truthfully in front of a grand jury.

He has been living in the UAE, where he has established deep connections to the royal court, since 2018. His apartment in Washington, D.C, was cleared out last summer, according to an eyewitness, his things removed in trash bags, including a toilet.

It is unclear why he returned to the U.S. on Monday.