George Nader, who was a key witness in Special Counsel Robert Mueller’s investigation, was hit with new federal charges of sex trafficking for allegedly “engaging in sexual acts” with a 14-year-old boy he transported from Europe.

An indictment unsealed Friday morning in Eastern District of Virginia also charges Nader with counts of child pornography and obscenity. The charges come on top of separate child-porn charges leveled by the same prosecutors last month.

Nader pleaded not guilty to all charges during a court appearance Friday.

Nader, a 60-year-old Lebanese-American businessman with deep political and financial ties to the United Arab Emirates, was a key cooperator in Mueller’s probe of foreign influence in the 2016 election. Nader met several times with individuals associated with the Trump campaign throughout the election and into the early days of the administration. He spoke with officials and advisers on matters ranging from a pitch by a foreign firm for the campaign to use social-media manipulation to regime-change in Iran. (He met with Donald Trump Jr. and other campaign advisors about the plan, which included a proposal to use fake avatars to garner support for Trump, but Trump officials deny they ever considered it.)

He also helped broker a key meeting between Erik Prince, the former Blackwater CEO, and Kirill Dmitriev, the head of one of Russia’s sovereign wealth funds, in the Seychelles in January 2017. That meeting came under intense scrutiny by Mueller’s team and was described in its report as one of the ways the Russians tried to influence the incoming Trump administration.

Federal prosecutors in Virginia argued last month in court that Nader should be held in jail before trial, based in part on his prior criminal history. That history includes a 2003 conviction in the Czech Republic on charges of abusing minors, including a charge of transporting of a minor boy to the U.S. for sexual purposes. Federal prosecutors said Nader has had “hands-on contact with more than a dozen minor boys.” Nader’s lawyers called the U.S. government’s argument weak because he was later acquitted of the Czech sex-trafficking charge.

Nader is also charged with transporting child pornography—a charge he’s faced in the past. In 1984, Nader was indicted for possessing child pornography in D.C. The charge was later dismissed after his attorneys argued that the material was found through an illegal search conducted on Nader’s possessions at Dulles. In 1990, again at Dulles, law enforcement caught Nader with films featuring minor boys. Nader pleaded guilty the following year.

Nader most recently faced allegations of possessing and transporting child pornography in 2018. Authorities stopped him at Dulles in January of that year and questioned him about his time working with the Trump team. Soon after, Nader began cooperating with Mueller, and in the spring of 2018 he departed for Dubai, where he lived until he attempted to re-enter the U.S. last month.

When stopped at Dulles, the FBI executed a search warrant on Nader’s electronic devices, including three iPhones. After analyzing the phones, the FBI found 12 videos that appeared “to be visual depictions of minors engaged in sexually explicit conduct,” according to a criminal complaint filed in 2018 that remained under seal until last month.

Nader is also charged with violating federal obscenity law.

On June 3, he was arrested at JFK International Airport in New York and transferred to a Virginia jail, where he remains locked up.

Last month, prosecutors told a court that FBI agents found dozens of child-porn videos on one of Nader’s phones, with some depicting children as young as 3 years old.

The FBI witness for the government said several of those videos were transmitted from Nader’s phone to other individuals. Prosecutors said authorities also found communications between Nader and UAE Crown Prince Mohammed bin Zayed, also known as MBZ.

Nader’s attorneys said he returned to the U.S. for an urgent doctor’s appointment after undergoing major heart surgery in the UAE weeks earlier.