One of the most infamous terrorists of the 1980s has rejoined Hezbollah following his release from a German prison and deportation to his native Lebanon in December 2005, a senior Bush administration official told FOX News.

Mohammed Ali Hamadi was released despite strong U.S. objections, FOX News learned. Those objections were raised in phone calls to German authorities by Attorney General Alberto Gonzales and FBI Director Robert Mueller, as well as by top-level State Department and administration counter-terrorism officials.

"[The Germans] ignored us and didn't give us enough time to pursue it through legal action," an official told FOX News on the condition of anonymity. "They gave us very short notice."

U.S. officials said they "can't rule out" the possibility that Germany deported Hamadi, after he had served 19 years of a life sentence, in exchange for the release of Susanne Osthoff, a German archeologist taken hostage in Iraq and freed four days after Hamadi's deportation. German authorities have denied any such deal was made.

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In June 1985, Hamadi was one of four Islamic militants who commandeered TWA Flight 847 — en route from Athens to Rome — and hijacked it to Beirut. The ensuing hostage ordeal lasted 17 days, with the plane shuttling among various Mediterranean airports.

On the second day of the hijacking, Hamadi and his accomplices learned that U.S. Navy diver Robert Dean Stethem was on board. Hamadi and his co-conspirators beat Stethem unconscious, then shot him to death and dumped his body on the tarmac of the Beirut airport. The hijackers later escaped.

In 1987, Hamadi was arrested in Frankfurt, Germany, for carrying explosives in his bag at the airport. He was convicted both on that charge and of Stethem's murder and sentenced to life in prison. Late last year he was paroled by the German authorities and deported to Lebanon.

On Dec. 21, 2005, shortly after Hamadi's return to Lebanon, State Department spokesman Sean McCormack told reporters: "I think what I can assure anybody who's listening, including Mr. Hamadi, is that we will track him down, we will find him and we will bring him to justice in the United States for what he's done.

"We will make every effort, working with the Lebanese authorities or whomever else, to see that he faces trial for the murder of Mr. Stethem."

At a press briefing Tuesday, State Department spokesperson Tom Casey confirmed that contact had been made with the Lebanese government regarding Hamadi, and that the case remains active.

"The United States still believes that he and anyone else who is responsible for such heinous acts should face justice," Casey said. "And we do continue to wish to see him be brought to the United States to face trial here."

Hamadi's alleged accomplices — Hassan Izz-Al-Din, Ali Atwa and Imad Mughniyeh — were never captured.

Mughniyeh is also believed to be responsible for the 1983 barracks bombing that killed 241 U.S. Marines in Lebanon and for the 1984 torture and murder of William Buckley, the CIA Station Chief in Beirut.

Mughniyeh, who is believed to have undergone extensive plastic surgery to make himself unrecognizable, has been described in the media as "probably the world's most wanted outlaw."

Upon hearing news of Hamadi's release in 2005, Stethem's family members said they would keep pressuring the U.S. government to seek extradition from Lebanon.

"We'll be after him," Stethem's mother, Patricia, said of Hamadi. "We won't let it rest."

James Rosen joined Fox News Channel (FNC) in 1999. He currently serves as the chief Washington correspondent and hosts the online show "The Foxhole." His latest book is "A Torch Kept Lit: Great Lives of the Twentieth Century" (Crown Forum, October 4, 2016).