American Sgt. Bowe Bergdahl, while held prisoner in Afghanistan, was locked in solitary confinement for two straight years and did not see another human face for that entire time, senior military sources with knowledge of his "reintegration process" told Fox News.

Officials said Bergdahl, during that period, only talked to his captors through the wall of a six-foot-by-six-foot metal box, in which he was kept.

The box was just big enough for him to stand up straight and stretch his arms. If he was ever taken out of the box, Bergdahl was apparently hooded. Bergdahl told officials that this treatment started immediately after he attempted to escape captivity.

"His mental and physical state match this description -- and we believe him from what we see," one official told Fox News.

The details emerged as Bergdahl arrived early Friday at an Army medical center in San Antonio, Texas.

Officials there told a Friday afternoon press conference there is no timeline for Bergdahl’s reintegration, but added that he was in stable condition and that they hope he will “transition to a normal healthy lifestyle.”

Army South Commander Major General Joseph DiSalvo said the reintegration process is to help Bergdahl “with the necessary tools to regain appropriate levels of physical and emotional stability to effectively resume normal activities with minimal physical and emotional complications.”

DiSalvo added that Bergdahl is currently in “stable condition and will work daily with medical and mental health professionals.”

Bergdahl was captured in Afghanistan in June 2009 and released on May 31 in a deal struck by the Obama administration in which five Taliban officials were released from detention.

A Pentagon spokesman, Rear Adm. John Kirby, said Bergdahl arrived at Brooke Army Medical Center in San Antonio on a flight from Ramstein Air Base. The 28-year-old Idaho native was expected to be reunited there with his family.

"Our focus remains on his health and well-being," Kirby said, adding that Defense Secretary Chuck Hagel is confident that the Army will continue to ensure that Bergdahl receives the care, time and space he needs to reintegrate.

Bergdahl's family, meanwhile, have asked for continued privacy in a statement released Friday on their behalf by military officials.

"While the Bergdahls are overjoyed that their son has returned to the United States, Mr. and Mrs. Bergdahl don't intend to make any travel plans public," the statement reads. "They ask for continued privacy as they concentrate on their son's reintegration."

Army psychologist Col. Bradley Poppen said during Friday’s news conference that it’s typically up to the soldier to determine when to reunite with his or her family.

It's unclear known how long Bergdahl will remain there or if and when he will be questioned about the circumstances behind his apparently voluntary departure from an Army base in Afghanistan in 2009.

Fox News' Bret Baier and The Associated Press contributed to this report.