There are multiple reports citing Iranian media that four American citizens who have been held in Iran either have been, or will be, released:

From Reuters:

Iran has released four prisoners with dual Iranian-U.S. nationality, the Tehran public prosecutor was quoted as saying on Saturday, without giving further details.

“In line with orders from the Supreme National Security Council and in the national interest, four Iranian dual national prisoners have been released in a prisoner swap,” Abbas Jafari Dowlatabadi was quoted as saying by Iranian news agencies.

The release is reportedly part of a prisoner swap:

The report about the release of prisoners comes shortly after Iran detained ten U.S. sailors and used photos of their arrest for propaganda purposes.