Another twist in the story of Iranian-Turkish billionaire Reza Zarrab and his ties to the Turkish government may be in cards, with new speculation that he is cooperating with US prosecutors.

Bloomberg is reporting that Zarrab was suddenly released from prison last week, government records showed, but that two people familiar with the matter say he remains in US custody, though not in federal jail. This sometimes happens when a defendant agrees to serve as a government witness, the report noted.

Zarrab is accused of helping Iran evade sanctions through a money-laundering scheme. Earlier this month, documents revealed that US prosecutors say the scheme was supported by the Turkish government and that Zarrab had invoked President Erdogan’s name in recordings related to the alleged crimes.

The case goes back at least until 2013, when Zarrab was implicated in a corruption probe initiated by Turkish authorities, but Erdogan effectively put an end to the investigation during a purge of Turkey’s judiciary. The same evidence that was uncovered by Turkish investigators at the time, which threatened to expose details of government officials’ financial dealings with Iran, may now be used by US prosecutors in the trial set to begin Monday in New York.

The Erdogan regime has characterized the US investigation as a plot to undermine Turkey’s economy and has repeatedly lobbied Washington to drop the case.

There is also no shortage of intrigue on the US side of the case, where two close Trump associates – including former New York City Mayor Rudy Giuliani – are on Zarrab’s defense team. Giuliani advised Trump during his transition and sought to broker an end to the case after meeting with Erdogan. The case was originally brought by Manhatten US Attorney Preet Bharara, who was fired shortly after Trump took office.