WASHINGTON - U.S. officials are interrogating Iraqi officials who have been taken into custody and some of them are "providing information that is useful," Defense Secretary Donald Rumsfeld said Friday. 

Rumsfeld told a Pentagon briefing that between 7,000 and 7,500 Iraqis have been taken prisoner, but that lower-level ones like foot soldiers are being released. 

Among those held, Rumsfeld said, were "12 of the 55 most-wanted officials ... as well as a number of others who were not on that list." 

He said they are being held in various locations. The Pentagon has no plans to send any of them to its prison facilities at Guantanamo Bay in Cuba, where captured Taliban and al-Qaida fighters are being held from the war in Afghanistan, he said. 

Rumsfeld expressed satisfaction that Tariq Aziz, the former deputy prime minister under Saddam Hussein, was among those in custody. Aziz surrendered on Thursday. 

A top Iraqi intelligence officer was the latest apprehension confirmed Friday. 

Aziz "clearly is a very senior person and was in that regime and we intend to discuss with him whatever he's willing to discuss with us," Rumsfeld said. 

Aziz's prominence in the regime could make him a source for the best information yet on the fate of Saddam and his two sons, as well as the location of any hidden weapons of mass destruction. 

Asked whether fugitive Iraqi leaders might be hiding together, Rumsfeld said that to suggest they were all in one place "would be clearly not the case." 

"I would guess that some got over the border and are finding haven in some place. Others we found and still others are in the country in various places trying to be inconspicuous and we'll eventually find them," he said. 

Rumsfeld said that along with the Iraqis taken into custody were some Syrians who were "in there doing things they shouldn't have been doing." 

Overall, "We're keeping the hard cases separate for the most part. We're systematically going through less-hard cases and releasing people." He said about 1,000 had been released so far. 

"We obviously don't want to hold any more people than we have to," Rumsfeld said. 

White House spokesman Ari Fleischer said earlier Friday that Aziz's capture "portends for a stronger future for the people of Iraq, a future of freedom as vestiges of the Baath regime are captured or turn themselves in and we welcome this capture." 

The capture of top Iraqi figures could prompt other wanted officials to turn themselves in, Pentagon officials said. Information from the others already in custody also could lead to more on the wanted list, the officials said. 

Aziz was No. 43 on the U.S. most-wanted list, the eight of spades in the military's card deck of top Iraqi leaders. 

On Friday, a U.S. official confirmed that former Iraqi senior intelligence operative Farouk Hijazi has been captured by U.S forces in Iraq. 

Hijazi is Iraq's ambassador to Tunisia and was not among the top officials in the deck of cards. But Hijazi, who also has served as Iraq's ambassador to Turkey, still is considered a prize catch. 

Hijazi allegedly met with Osama bin Laden in Kandahar, a region in southeastern Afghanistan where al-Qaida had training camps, U.S. officials have said. It's not known what might have been discussed at the December 1998 meeting. Iraqi officials denied Hijazi met with bin Laden. 

As for Aziz, he was the only Christian in Saddam's inner circle, most of whom were Sunni Muslims like Saddam. He served as foreign minister during the 1991 Persian Gulf War and was a frequent spokesman at that time. 

With his flawless English, the silver-haired Aziz also frequently represented his government's views to Western media, denouncing the United States and insisting Iraq had no chemical, biological or nuclear weapons. 

He last appeared in public March 19, when he held a news conference in Baghdad to quash rumors he had fled the Iraqi capital. 

"I am carrying my pistol to confirm to you that we are ready to fight the aggressors," Aziz said then. "American soldiers are nothing but mercenaries and they will be defeated." 

Although he was one of Saddam's most loyal aides, Aziz, like most who were not from Saddam's Tikriti clan, had virtually no power, U.S. officials have said. That could explain his longevity in Saddam's inner circle - without an independent power base, he posed no threat. 

Saddam promoted him after the Gulf war to deputy prime minister, forcing him to relinquish the foreign ministry portfolio. Some believe this reshuffle had to do with Saddam's discomfort with Cabinet ministers who became too well known.