Spanish authorities did not say whether the Algerian's prints were the only prints on the bag. U.S. officials have previously said Mayfield's prints were on the bag.

However, Mayfield's release on Thursday brought new scrutiny of the material witness statute, under which the attorney was held without being charged since May 6.

"It's a huge embarrassment for the Justice Department," said Michael Greenberger, a former senior U.S. Justice Department official who now heads the University of Maryland's Center for Health and Homeland Security.

The Justice Department has portrayed the material witness statute as a powerful tool to round up terrorists, giving authorities the right to jail suspects for weeks or months in complete secrecy.

Civil rights groups have said the net is cast too broadly, and innocent U.S. citizens are now simply disappearing into jails with no accountability, or right to mount a defense.

Grasping a Quran and a Muslim prayer rug, 37-year-old Brandon Mayfield was freed on the steps of the federal courthouse in Portland after a detention hearing.

According to the U.S. District Court's Web site, Mayfield was ordered released "pending further grand jury proceedings wherein he remains a material witness."

Holding his wife Mona's hand on the steps of the courthouse, Mayfield called his two weeks in the Multnomah County jail "a harrowing ordeal."

In Arabic and then in English, Mayfield, a convert to Islam, recited the Muslim prayer: "God is great. There is no God but God."

Within two days of his arrest, Spanish officials began to voice strong doubts that the fingerprint found on the bag was really his.

Spanish investigators told the Madrid newspaper El Pais that they had found only eight points of similarity between the print and Mayfield's - instead of the 15 required for an exact match. In addition, Mayfield's family challenged authorities to check his passport - saying the attorney had not been out of the country in at least 10 years.

U.S. Public Defender Steve Wax said that a gag order issued by a federal judge remained in place, preventing officials here from discussing details of Mayfield's release.

Beth Anne Steele, a spokeswoman for the FBI in Portland, said she could not comment because "it is a pending grand jury matter."

Samer Horani, a board member of the Islamic Center of Portland, called Mayfield's arrest and subsequent release a stark example of the FBI's profiling of Muslims.

"Ethnicity doesn't matter. If you are Muslim you are suspect," he said.

In Madrid late Thursday, authorities said the fingerprints found on the plastic bag belonged to an Algerian, Ouhnane Daoud.

"The extensive and meticulous work of the Spanish scientific police has determined completely that the fingerprint identifications are of the medium and thumb fingers of the Algerian's right hand," Spanish authorities said.

After his release, Mayfield went to his home in Aloha, a suburb of Portland.

Mayfield's mother was there waiting for him.

"I'm just elated," said his 63-year-old mother, Avnell Mayfield in a telephone interview. "He's much taller than I remember him being."

His children gave him the gifts they had made for him - origami boxes, lemon cookies, a sewing project.

Samir, 10, and Sharia, 12, had started crocheting yellow and tan socks, but had not finished them in time for their father's surprise release. "Dad, you got out sooner then we thought," the 10-year-old told him, according to Mayfield's mother.

Tom Nelson, an attorney and Mayfield's legal mentor, said the FBI has a lot of explaining to do.

"Even if the angels came down from heaven and sung his praise, it wouldn't remove this stain," said Nelson. "We need to think now of how we get back to normal - what is this going to do to his long-term client base?"