The men were abducted in two separate incidents that occurred a month and a half apart more than two years ago, a U.S. government official said Thursday in Washington.
The Austrian weekly magazine News first reported the delivery of the five fingers in Wednesday's edition, citing unidentified authorities working on the case.
Patrick Reuben, a Minneapolis police officer whose twin brother, Paul Reuben, is among the missing, said late Wednesday the FBI told his family members that "the fingers were confirmed to be those of the hostages."
Patrick Reuben said the news of the severed fingers was "shocking," but that the initial word the family got was "much more serious than that. Later on we found that it was fingers that were recovered and that the DNA confirmed it was the hostages."
The fifth, Ronald J. Withrow, 40, of Lubbock, Texas, was a contractor working for JPI Worldwide and abducted on Jan. 5, 2007 near Basra.
In addition to Reuben, those abducted in the earlier incident were Jonathon Cote, 25, of Getzville, New York; Joshua Munns, 25, of Redding, California; and Bert Nussbaumer, 26, of Vienna, Austria, said the U.S. government official in Washington. The official spoke only on condition of anonymity because he was not authorized to speak on the record about the matter.
A fifth hostage taken in the Nov. 16, 2006 ambush was John Young, 45, of Lee's Summit, Missouri. None of his fingers was sent to the U.S. military.
In a statement, the FBI declined to confirm the men had been identified by fingers.
"The FBI has received DNA evidence and is conducting an examination," spokesman Richard Kolko said. "We understand this is a very difficult time for the families and discussing this matter further in the media is not appropriate."
The four men kidnapped in the Nov. 16, 2006 incident were working for Crescent Security Group, a Kuwait-based private security company. Men in Iraqi police uniforms ambushed a convoy near the southern city of Safwan.
Patrick Reuben said his family is "certainly hopeful, but there's nothing definite right now."
The father of Cote said he and other families were visited by the FBI two to three weeks ago, when they were told DNA samples had been identified as those of the hostages. The agents would not say how they had gotten the samples.
When Francis Cote read a news report about the fingers, he contacted the State Department but was given no confirmation or denial.
"They told us the FBI would visit us," Cote said.
Cote received calls Wednesday from Paul Reuben's wife, who was in tears, and Munns's mother. The hostages' families frequently contact each other to share news and compare notes, he said. Cote assured the women that the hostages were still alive.
"It's possible they did sever (the fingers) to show proof of life," Cote said. "I'm sure somebody from our government was asking for proof of life and I guess proof of life was severing a finger versus delivering a video."
Cote said he was frustrated by the government's reticence.
"We have no news, we have activity," has been the extent of officials' comments on the hostages for months, Cote said. "It's very vague."
Police. Col. Rudolf Gollia, a spokesman for the Austrian Interior Ministry, said the report that the severed fingers had been sent to U.S. authorities was being treated as a rumor.
He said U.S. officials in Baghdad forwarded information to the Austrian Embassy in Amman, Jordan, that the Americans described only as "based on fingerprints and DNA profiles."
He said Austrian officials were trying to get more information from U.S. officials and other sources in the Middle East.