Saddam Hussein's half brother, one of 55 people on a U.S. most-wanted list, has been captured in Iraq near the Syrian border and is in U.S. custody, officials said on Sunday. Watban, Saddam's half brother from his mother's second marriage, was a presidential adviser. But U.S. officials said he was not close to the Iraqi leader, whose government has now collapsed, because Saddam harbored suspicions about Watban's loyalty.

"He and Saddam were estranged, they were not close," one official said. "Saddam was very suspicious of him, thought he was disloyal and kept him on a very tight leash."

Information Watban could provide to the United States might include insights about the family, their residences and where those who survived the war might flee, U.S. officials said.

War commander Gen. Tommy Franks told CNN on Sunday that U.S.-led forces had DNA genetic material that could be used to identify Saddam and check whether attempts to kill him had succeeded.

There was speculation that Watban may be the source of the DNA, although that was not confirmed. "That would be like a walking supply of DNA," another official said.

One of Saddam's three younger half brothers, Watban was made interior minister in 1991 and hailed by state media as the man who would stop soaring crime blamed on U.N. economic sanctions after the Gulf War. At the time, the post was the second most powerful in the cabinet after defense minister.

But he was dismissed in 1995 following repeated attacks on the police in the newspaper Babel, which was published by Uday -- Saddam's influential eldest son.

Later that year, Watban was injured in a mysterious shooting at a party outside Baghdad, which fueled rumors of family feuding amid reports he was shot in the leg by Uday.

On Saturday, Saddam's top scientific adviser, Amer Hammoudi al-Saadi, surrendered to U.S. troops and U.S. officials hope he will unlock secrets about Iraq's weapons. Baghdad consistently denied it had such weapons.

U.S. officials also said on Sunday that a top Iraqi nuclear scientist, Ja'far al-Ja'far, had surrendered to U.S. authorities outside Iraq.

It could not immediately be determined in which country he had surrendered. But officials said it was not Syria, where the United States suspects some Iraqi leaders may have fled.

The fate of Saddam and his sons Uday and Qusay remained a mystery after two separate U.S. bombings of sites where they were believed to have been.