Relations between Turkey and the United States hit another bump this week when Ankara issued a diplomatic note formally requesting information from US officials on the whereabouts of a Turkish gold trader jailed in New York in a case that has roiled ties between the NATO allies.

Reza Zarrab, a Turkish-Iranian facing charges for allegedly violating US sanctions on Iran, is at the center of a political tug of war. Turkish President Recep Tayyip Erdogan accuses the United States of having ulterior motives in bringing the case against the businessman who once fraternized with ministers in his government.

The Foreign Ministry sent the note Wednesday after Zarrab’s lawyer was unable to contact him and the US Federal Bureau of Prisons’ website indicated he had been released from prison. The New York attorney general’s office said Zarrab remains in custody, newspapers reported.

The latest twist comes just as the two countries seemed to be trying to mend a relationship that hit bottom last month when the United States halted non-immigration visa services in Turkey following the arrests of local consular staff members. The State Department partially restarted issuing visas on the eve of a visit to Washington by Prime Minister Binali Yildirim.