The Turkish Foreign Ministry issued a second diplomatic note to the U.S. regarding Turkish-Iranian gold trader Reza Zarrab's whereabouts after the first note was left unanswered, the foreign minister said Thursday.

Mevlüt Çavuşoğlu told reporters that the first diplomatic note about Zerrab's condition was issued three or four days ago and the Turkish authorities pushed the U.S. once again to receive an answer.

On Wednesday, Turkey issued a note, urging the U.S. to notify Turkish authorities before relocating Turkish detainees to different facilities. The ministry noted that Zarrab was recently threatened in a federal holding facility, which necessitated moving him to a different facility.

It highlighted the importance of the U.S. State Department's assistance in notifying the Turkish embassy and their attorneys as soon as possible when Turkish citizens are moved to a new location as well as the reasons for such a decision.

In the note, the ministry asked the whereabouts of the businessman, who was arrested in Miami last year over accusations of engaging in hundreds of millions of dollars-worth of transactions on behalf of the government of Iran and other Iranian entities, which were barred by U.S. sanctions, while laundering the proceeds and defrauding several financial institutions by concealing the true nature of the illegal transactions.

His lawyer said that he cannot communicate with Zarrab, who is standing trial in New York, and the Attorney General's Office does not provide his specific whereabouts and the state of his health.

The office told Daily Sabah that Zarrab is in federal custody.

U.S. prosecutors also charged the former Turkish economy minister Zafer Çağlayan, who is also the former general manager of state-owned Halkbank, Süleyman Aslan, and two others for conspiring to evade U.S. sanctions against Iran.

The indictment broadens the case targeting Zarrab over sanction evasion, which has fueled tensions between the U.S. and Turkey. Zarrab and a Halkbank deputy general manager, Mehmet Hakan Atilla, were both arrested while in the U.S. in March 2016 and are scheduled to stand trial in October. If convicted, they face prison terms of up to 30 years.