The top Democrat on the Senate Foreign Relations Committee called on Iran to release other imprisoned Americans after Tehran freed a Chinese American graduate student on Saturday as part of a prisoner exchange.

Sen. Bob Menendez Robert (Bob) MenendezWatchdog confirms State Dept. canceled award for journalist who criticized Trump Kasie Hunt to host lead-in show for MSNBC's 'Morning Joe' Senators ask for removal of tariffs on EU food, wine, spirits: report MORE (D-N.J.), the ranking member of the Foreign Relations panel, lauded the release of Princeton University scholar Xiyue Wang but said Tehran must release other Americans held in Iranian prisons.

“Tragically, Iran continues to pursue unjust, political detentions of its own citizens, Americans, and other foreigners. While we celebrate the release of Mr. Wang we cannot forget Robert Levinson, Michael White, and Baquer and Siamak Namazi and others unjustly detained,” the senator said in a statement.

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Menendez has been a vocal advocate of efforts to free the detained Americans, introducing the Robert Levinson Hostage Recovery and Hostage-Taking Accountability Act to bolster government programs to address hostage taking.

Administration officials maintained that after Wang’s release they will continue to advocate for the freeing of Americans imprisoned around the world.

“The highest priority of the United States is the safety and well-being of its citizens. Freeing Americans held captive is of vital importance to my Administration, and we will continue to work hard to bring home all our citizens wrongfully held captive overseas,” President Trump Donald John TrumpBiden says voters should choose who nominates Supreme Court justice Trump, Biden will not shake hands at first debate due to COVID-19 Pelosi: Trump Supreme Court pick 'threatens' Affordable Care Act MORE said in a statement.

“We continue to call for the release of all U.S. citizens unjustly detained in Iran,” added Secretary of State Mike Pompeo Michael (Mike) Richard PompeoWatchdog confirms State Dept. canceled award for journalist who criticized Trump Trump's push for win with Sudan amps up pressure on Congress Putin nominated for Nobel Peace Prize MORE.

A senior administration official told reporters Saturday that they hoped Wang's release marked an openness by Iran to abandon what they called "hostage-taking diplomacy" on the part of Tehran.

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The family of Robert Levinson, considered to be the longest-held hostage in U.S. history, said they were “extremely disappointed” that he remains imprisoned. He has been held in Iran for nearly 13 years.

“We welcome the release of Xiyue Wang and send our best wishes to him, his wife, Hua Wu and their young son, who will finally get to see his father again. This is a day they have long hoped for, but this news is bittersweet for our family,” the family said in a statement. “We can't help but be extremely disappointed that, despite all its efforts, the United States government was unable to secure his release, especially after such a painful week for our family.”

“It is time for Iran to send Bob Levinson home, so he can live the rest of his life in peace. We look forward to when that day will come,” they added.