According to Reuters, Penn flew to Venezuela to ask President Hugo Chavez to intervene in the case with Iran's Mahmoud Ahmadinejad.
Shane Bauer and Josh Fattal were freed on Wednesday. A third hiker, Sarah Shourd, was released on humanitarian grounds after a year in prison.
Bauer and Shourd have another reason to celebrate: Bauer became officially engaged to Shourd on Friday. Both became engaged in prison where Bauer made his fiancée a ring from threads of string removed from a shirt.
On Friday, Bauer gave Shourd a more traditional ring.