The FBI and other authorities are investigating threats against the family of Army Sgt. Bowe Bergdahl, the American soldier released nine days ago in a deal that also freed five detainees from the U.S. detention center at Guantanamo Bay.
William Facer, FBI spokesman in Salt Lake City, said in a statement that the agency is "working jointly with our state and local partners and taking each threat seriously."
Bergdahl, 28, was held captive by the Taliban-aligned Haqqani network in Afghanistan for five years. The deal for his release has drawn criticism as reports surface that he had become disillusioned by the war and had walked away from his post prior to his capture.
Facer did not detail the threats. Bergdahl hails from Hailey, Idaho, and his parents, Bob and Jani Bergdahl, still live there. Last week city officials abruptly canceled a welcome-home celebration for Bergdahl, citing security concerns.
Mayor Fritz Haemmerle said the city has been deluged with angry mail and phone calls.
"The city of Hailey respectfully requests that people do not pre-judge this young man," Haemmerle said in a statement issued Monday. "The city of Hailey believes in due process, and we are very happy to let the process unfold."
Two days later the event was called off.
"Hailey, a town of 8,000, does not have the infrastructure to support an event of the size this could become," Haemmerle said.
The prisoner swap also drew withering criticism on Capitol Hill, where Republicans led the charged. Sen. John McCain, R-Ariz., has argued that the five freed detainees are terrorists who could again wage war on Americans.
The White House has said it made the deal out of concern for Bergdahl's health, which it said was declining rapidly in captivity. President Obama also stressed that it was U.S. policy to bring everyone home from Afghanistan, especially now with the war winding down.
The Army has said it will investigate the circumstances surrounding Bergdahl's capture.
Bergdahl remains hospitalized at a U.S. base in Germany. Details of his condition have not been released.
Contributing: Associated Press