The author of a best-selling book about his father and other men who raised a U.S. flag at Iwo Jima during World War II said Tuesday he no longer believes his father was in an iconic photograph of the event.

James Bradley, who wrote the book "Flags of Our Fathers," said in a telephone interview that questions raised about the photo by two amateur historians, which have prompted a Marine Corps investigation, led him to think back on comments his father made about the 1945 flag-raising. Those comments by John Bradley, who died in 1994, now lead James Bradley to believe his father participated in an earlier flag-raising, but not the one captured in the famous picture.

"My father raised a flag on Iwo Jima," Bradley told The Associated Press. "The Marines told him way after the fact, 'Here's a picture of you raising the flag.' He had a memory of him raising a flag, and the two events came together."

AP photographer Joe Rosenthal shot the photo on Feb. 23, 1945, on Mount Suribachi, only days into a bloody battle with the Japanese that would stretch on for weeks. The picture was displayed on front pages of newspapers across the U.S., later was used in a war bond sale and was depicted in the Marine Corps War Memorial in Arlington, Virginia.

Since 1947, the Marines have identified the Iwo Jima flag-raisers as John Bradley, Rene Gagnon, Ira Hayes, Harlon Block, Michael Strank and Franklin Sousley. All were Marines except Bradley, who was a Navy corpsman.

On Monday, the Marine Corps announced it had begun investigating whether it mistakenly identified one of the men after history buffs Eric Krelle, of Omaha, Nebraska, and Stephen Foley, of Wexford, Ireland, began raising doubts about the matter. They argued that the man believed to be Bradley actually was Sousley, and that the person for decades thought to be Sousley was Harold Henry Schultz, who previously wasn't thought to have any connection to the flag-raising.

All of those involved in the flag-raising have died, including three who were killed in later fighting at Iwo Jima.

Bradley, whose book was made into a movie directed by Clint Eastwood, said misidentifying the men who joined in the second flag-raising would be an easy mistake.

"The key is, no one was keeping track," he said. "There was the fog of war, post-traumatic stress."

Bradley said after reviewing his father's statements and photographs from that day on Mount Suribachi, he's confident his father wasn't in the famous picture, but it's impossible to be 100 percent certain.

"I know what these guys look like. I've studied them for years," he said. "But I could be wrong."