Reza Zarrab
Detained businessman Reza Zarrab (C) is surrounded by journalists as he arrives at a police center in Istanbul on Dec. 17 ,2013. Getty Images/ OZAN KOSE

As part of special counsel Robert Mueller’s probe into former National Security Adviser Michael Flynn, Mueller will be looking into an offer of $15 million made to Flynn by Turkish officials to arrange the release of, among others, Reza Zarrab.

Zarrab, a Turkish-Iranian businessman, reportedly boasted about having exported 200 tons of gold to Iran and earning more than $11 billion, in spite of the knowledge that the trades he carried out were banned by virtue of the sanctions imposed by the United States on Iran, International Policy Digest reported. He also allegedly bribed two Turkish ministers and the minister for EU affairs with $66 million.

Zarrab was arrested in Miami in March 2016, when he was on his way to visit Disneyland with his wife and daughter and charged with the violation of the U.S. and international sanctions, bank fraud and money laundering. Part of the charges was also due to the fact that exchange houses and front companies controlled by Zarrab laundered Iranian oil proceeds received from Halkbank (a Turkish state-owned bank), which was used for buying gold and exporting it to Iran from Turkey.

Zarrab’s arrest led to the relationship between U.S. and Turkey to go bitter, causing Turkish President Recep Tayyip Erdoğan to reach out to then Vice President Joe Biden to discuss the release of the business mogul. Since then, Turkish Justice Minister Bekir Bozdag met with his U.S. counterpart Loretta Lynch in October 2016, in an attempt to get her to drop the case. Erdoğan also raised the matter in talks with President Donald Trump in May.

Meanwhile, Zarrab’s current whereabouts are currently unknown, which is not usual for an alleged international criminal whose trial is due to begin in just days. According to the Daily Beast, Zarrab was released from the Bureau of Prisons on Nov. 8. Before that, he was being held at the Metropolitan Correctional Center, a federal administrative prison in New York City.

No court documents were filed by Zarrab in October. Last month Zarrab’s co-defendant, Deputy General Manager of Halkbank Mehmet Atilla appeared before the court alone and his lawyer remarked at the time that it seemed "likely that Mr. Atilla will be the only defendant appearing at trial."

To make matters more mysterious, Zarrab’s lawyer, Benjamin Brafman told the Daily beast that his client will not be showing up for the final pre-trial date set for Thursday. Nick Biase, a spokesman for the U.S. attorney’s office for the Southern District of New York has, however, assured that Zarrab has not gone missing from federal custody. "All I can tell you is that he is in federal custody."

It might be important to note that in high stakes cases such as Zarrab’s it is not unusual for inmates to be moved to different holding facilities before the trial begins. "It can be a challenge to work with them as a cooperator in a more active way," Renato Mariotti, a former assistant U.S. attorney, said. "Maybe he’s spending time in a hotel suite with some FBI agents, or in their local lockup."

According to Turkish news outlet Daily Sabah, the Turkish foreign ministry issued a diplomatic note to its U.S. counterpart, requesting them to notify Turkish authorities before relocating Turkish detainees. The note also mentioned that Zarrab was being threatened in a federal facility that he was being held. It is not clear whether Zarrab was relocated because of that reason or whether the U.S. foreign ministry heeded its Turkish counterpart’s request.

Mueller is currently looking into the possibility of Flynn discussing the Zarrab case with Turkish officials. Flynn confessed he worked as a paid agent for Turkey after he was forced to resign from his post of National Security Adviser to Trump in March.