James Nolan, 21, of Blessington, County Wicklow, disappeared early Sunday in the northern city of Bydgoszcz, sparking a huge search effort in the city. Police divers found a body early Wednesday and authorities are awaiting the arrival of Nolan's father, Jimmy, and other family members later in the day to make a formal identification.
"There is a high probability that this is the body of the man we have been searching for," a spokesman for prosecutors, Jan Bednarek, told The Associated Press.
The body was found lying face down in fast-flowing water of the Bydgoszcz Canal and trapped by a weir that runs across it. The canal is an offshoot of the city's Brda River, and brings water for a small hydroelectric plant.
No signs of violence were apparent, deputy chief prosecutor Wlodzimierz Marszalkowski told The Associated Press. Robbery didn't appear to be the motive since 600 zlotys ($200) and a credit card were found on the corpse, he said. An autopsy was planned for Thursday.
The clothing on the body matched a description given by friends of what Nolan was wearing when he went missing, officials said.
Police and firefighters, some in boats and others with dogs, had been searching along the river, canal and adjacent waste ground Tuesday and again on Wednesday.
Moments before the body was found, two divers in an inflatable dinghy were seen speeding toward the site. A police cordon was quickly set up around the area, which is near a museum and a church.
Nolan was in Poland for Euro 2012 to follow Ireland, which has now been eliminated from the soccer tournament. He had been traveling with friends in a rented camper van, but was also registered at a hotel on the city's outskirts.
He was last seen visiting local bars after watching televised games in a fan zone Saturday night.