Iran and the U.S. conducted a prisoner swap on Saturday, which saw the release of an American graduate student in return for an Iranian scientist held by Washington.

“Glad that Professor Massoud Soleimani and Mr. Xiyue Wang will be joining their families shortly,” Iranian Foreign Minister Javad Zarif said on Twitter.

“Many thanks to all engaged, particularly the Swiss government.”

Switzerland represents U.S. diplomatic interests in Iran, since Washington and Tehran severed diplomatic relations shortly after the 1979 Islamic Revolution in Iran.

Read more: Iran frees US student in prisoner swap