The Iraqis are being interrogated about Iraq's suspected chemical, biological and nuclear weapons programs, U.S. officials said Sunday. They also are being pressed for details on where Saddam is, if he is alive, as well as the whereabouts of other former Iraqi leaders. 

The captured Iraqis include Watban Ibrahim Hasan, one of Saddam's three half brothers, who once served as Iraq's interior minister. Hasan was the five of spades in the deck of playing cards the U.S. military issued with pictures of wanted Iraqi officials. 

The war's commander, Gen. Tommy Franks, said Sunday that the United States was holding several high-ranking Iraqi prisoners in western Iraq. Neither he nor Pentagon officials would say how many leading Iraqis have been captured. 

As the fighting in Iraq winds down, American forces are stepping up the search for the chemical and biological weapons the United States accuses Saddam's government of having stashed away. So far, no caches of weapons of mass destruction have been confirmed in Iraq, military officials said Sunday. 

U.S. forces have a list of 2,000 to 3,000 sites in Iraq that need to be checked, and weapons teams are checking up to 20 sites a day, Franks said. Iraqis ranging from common people to high-ranking officials have suggested other possible hiding places to be searched, Franks and other military officials said. 

"There are so many sites, we are not able to get to all of them right away," a senior Pentagon official said Sunday, speaking on condition of anonymity. "It's fair to say there are a lot of places U.S. forces are adding to the list." 

One former Iraqi official who could provide major help for the hunt is Lt. Gen. Amer al-Saadi, who surrendered to American forces on Saturday. Al-Saadi, the seven of diamonds in the U.S. deck of cards, was Saddam's point man on weapons of mass destruction before the Iraqi government collapsed. 

Pentagon officials said Sunday they did not know if al-Saadi was sticking to his prewar assertions that Iraq no longer had any chemical or biological weapons. Shortly before leaving his Baghdad villa Saturday with his German wife, Helga, and surrendering to an American warrant officer, al-Saadi insisted Iraq has no such weapons. 

Also unclear was how helpful Hasan, Saddam's captured half brother, could be. Hasan was dismissed as interior minister, the official in charge of Iraq's domestic security, and was shot by Saddam's son Odai in 1995 amid one of the many squabbles within Saddam's family. 

Saddam did not trust Hasan and was having him watched, a U.S. official said Sunday. He was captured near Mosul in northern Iraq, apparently as he tried to escape to Syria, the official said. 

Another half brother, Barzan Ibrahim Hasan, was targeted by a coalition airstrike Friday on a building in central Iraq. Military officials said Sunday they had not confirmed Barzan Hasan's fate. 

Other top Iraqi officials have escaped to Syria, Defense Secretary Donald H. Rumsfeld said. Some have moved on to third countries, he said. 

"We certainly are hopeful Syria will not become a haven for war criminals or terrorists," Rumsfeld said. 

President Bush also issued a vague warning Sunday to Syrian President Bashar Assad. 

"The Syrian government needs to cooperate with the United States and our coalition partners and not harbor any Baathists, any military officials, any people who need to be held to account," Bush told reporters on the South Lawn of the White House as he returned from Camp David. 

Syria's government and Saddam's regime both belonged to the Arab Baath Socialist Party until a bitter split in 1960. In recent years the two factions seemed to have worked out some of their differences. 

A Syrian diplomat who followed Rumsfeld on NBC's "Meet the Press," Imad Moustapha, said Rumsfeld's accusations were false, and it is the U.S. military's job to prevent fighters and military goods from entering Iraq. 

Rumsfeld and Franks said American forces in Iraq had captured or turned back several busloads of fighters coming into Iraq from Syria. Aboard one such bus, Rumsfeld said, U.S. troops found several hundred thousand dollars in cash and leaflets offering rewards to people who went into Iraq to fight the U.S.-led coalition. 

American troops also have found scores of vests filled with explosives and metal bearings that could be used by suicide bombers in Iraq, Rumsfeld and Franks said. Documents found at one site suggested 30 of the bomb vests were missing, Rumsfeld said. 

Franks said the United States has a DNA sample from Saddam to check against remains found that might be from the Iraqi president. Two Baghdad airstrikes targeted Saddam, but Rumsfeld and Franks said they did not know if Saddam was alive. 

"He's either dead or he's running a lot," Franks said on CNN's "Late Edition with Wolf Blitzer." 

Pockets of resistance, as well as Fedayeen Saddam "death squads," remain in Iraq, Rumsfeld said. 

"The war isn't over. There are still people being killed. We lost some people last night," Rumsfeld said on CBS' "Face the Nation."