Service director Jarek Cielecki, a Polish priest and close friend of John Paul II, travelled to Poland after hearing an onlooker had photographed the image.
Father Cielecki said he was convinced the picture showed the former pontiff.
"You can see the image of a person in the flames and I think it is the servant of God, Pope John Paul II," he said.
The image was continuously broadcasted on Italian TV and also posted on religious websites, causing some of them to crash as thousands logged on to view with their own eyes the eerie figure formed by the flames.
The bonfire was lit during a service at Beskid Zywiecki, close to John Paul's birthplace at Katowice, southern Poland, on April 2 - the second anniversary of his death.
Hundreds had attended the ceremony. Gregorz Lukasik, the Polish man who took the photographs, said: "It was only afterwards when I got home and looked at the pictures that I realised I had something.
"I showed them to my brother and sister and they, like me, were convinced the flames had formed the image of Pope John Paul II.
"I was so happy with the picture that I showed it to our local bishop who said that Pope John Paul had made many pilgrimages during his life and he was still making them in death."