Twenty-one-year-old James Nolan, who travelled to Poland to cheer on Ireland at Euro 2012, had gone missing after a night out with friends in the northern city of Bydgoszcz.
An official from the prosecutor's office told public television police found Nolan's documents on the body brought up from the Brda river, near where he had gone missing around 1am on Sunday after separating from his friends.
Another official added that official confirmation would not be provided until the family have had a chance to identify the body.
"I can confirm that the body of a young man was pulled out of the river by divers," prosecutor Len Bojarski said.
"At the moment, we suspect that it is the missing Irish fan. There is a chance that the family will arrive in Poland later today and we will ask them to identify the body. Then we'll know for sure," he said.