The gold was transferred to Iran by the government of South Africa, which had been holding onto the assets due to harsh sanctions meant to pressure Tehran to reign in its rogue nuclear program.

The gold appears to have been released as part of a sanctions relief package that will have awarded Iran nearly $12 billion in unfrozen cash assets by the time negotiations wrap up next week.

Iran received $4.2 billion in unfrozen assets under the 2013 interim agreement with the United States and was then given another $2.8 billion by the Obama administration last year in a bid to keep Tehran committed to the talks.

The State Department calculates that Iran will have received a total of $11.9 billion in cash assets.