Three of the American detainees released by Iran as part of a prisoner swap this weekend landed in Geneva Sunday, en route to a U.S. military base in Germany for medical evaluation. Naghmeh Abedini, wife of Iranian-American Christian cleric Saeed Abedini, confirmed the plane had touched down.

Abedini, former U.S. Marine Amir Hekmati, the Washington Post’s Tehran bureau chief Jason Rezaian and Nosratollah Khosravi-Roodsari were ordered freed by Iran Saturday in exchange for seven Iranians being held by the U.S. Released separately was student Matthew Trevithick. But the fates of three other Americans, including former FBI agent Robert Levinson, were unknown.

Abedini, Hekmati and Rezaian apparently were the three American ex-detainees aboard the plane that landed in Geneva, as Khosravi-Roodsari and Trevithick reportedly stayed behind.

U.S. President Barack Obama Sunday praised the agreement on the exchange of prisoners, calling it a “milestone” in American-Iranian relations. The release came just before the implementation of the Iran nuclear deal, which came after the International Atomic Energy Agency verified Tehran had dismantled much of its nuclear program, thus paving the way for the lifting of international economic sanctions.

“When Americans are freed and reunited with their families, that’s something that we can all celebrate,” Obama said Sunday, hailing the returns of Abedini, Hekmati and Rezaian. The president praised Abedini for his “unyielding faith,” described Rezaian as a “courageous journalist” and cited Hekmati, who had been held for 4 1/2 years. He called their release the end of a “nightmare.”

Obama also said: “Iran has agreed to deepen our coordination as we work to locate Robert Levinson — missing from Iran for more than eight years. Even as we rejoice in the safe return of others, we will never forget about Bob. Each and every day, but especially today, our hearts are with the Levinson family, and we will not rest until their family is whole again.”