WARSAW, Poland — Prosecutors in Poland and Germany said Tuesday they are reviewing files on a Minnesota man who was a commander of a Nazi-led unit to see if they have enough evidence to press charges and request his extradition from the United States.

An Associated Press investigation revealed that Michael Karkoc, 94, entered the U.S. in 1949 by lying to American authorities about his leadership role in the SS-led Ukrainian Self Defense Legion, which is accused of torching villages and killing civilians in Poland during World War II. AP's evidence indicates that Karkoc was at the scene of the massacres, although no records link him directly to atrocities.

Robert Kopydlowski of Poland's National Remembrance Institute, which investigates Nazi and Soviet crimes, said prosecutors are reviewing files on Karkoc's unit for any evidence that would justify charges and an extradition request. Kopydlowski said the files were gathered during separate investigations into the killings of civilians in the village of Chlaniow, in southeastern Poland, and into Nazi suppression of the 1944 Warsaw Uprising against German occupation. The AP found documentation showing that Karkoc's unit was involved in both.

"If we have a living person who might be the perpetrator of a crime, we must gather evidence to prove that the person indeed took part in the crime and decide whether the evidence is sufficient to press charges and to seek an extradition," Kopydlowski said.

Kopydlowski said the institute had been aware of a commander named Karkoc from old records, but until the AP investigation had not known he was alive.

German prosecutors said they, too, were examining evidence and had contacted prosecutors in the United States and Poland about the case. On Tuesday, the U.S. Justice Department declined to comment on the matter.

"We know who he is. We know where he lives. Now we will look at the documents and check what investigations we've already opened against his unit," said Thomas Will, deputy head of the German office that investigates Nazi war crimes. He suggested it could be weeks before a decision is taken.

Phillip Villaume, a Minneapolis attorney hired by Karkoc's family, did not immediately return a call seeking comment on the developments in Poland and Germany.

Will and Kopydlowski both said the scarcity of living witnesses poses a problem for prosecutors. If European authorities decide to prosecute, Karkoc's U.S. citizenship could also make extradition difficult, Will said.

"Another hurdle is of course the health situation of an elderly man," he said.

Germany has taken the position that people involved in Nazi crimes must be prosecuted, no matter how old or infirm, as it did in the case of retired Ohio autoworker John Demjanjuk, who died last year at age 91 while appealing his conviction as a guard at the Sobibor death camp.