BRAINERD, Minn. (AP) — Officials of a Minnesota ice fishing tournament are investigating some of this year’s winners.

Officials with Brainerd Jaycees Ice Fishing Extravaganza say they’re investigating whether three men from Ohio legitimately caught the fish when they say they did, the Star Tribune reported.

Stephan Lyogky and his father, Ivan Lyogky, caught two of three northern pike that won prizes. A relative, Rostik Lyogky, caught the sole perch. The men finished in first, third and 98th place, respectively. Their prizes — a pickup truck, $1,000 and an ice auger — have been placed on hold.

A lawyer for the men said that they followed contest rules and are willing to take lie detector tests. Winning anglers who don’t take a test upon request must forfeit their prizes.

A message left by The Associated Press on Monday at a number listed for Ivan and Stephan Lyogky was not immediately returned.

Volunteers patrol the area on Gull Lake where anglers can fish, but with an estimated 12,000 participants this year, monitoring can be difficult.

It could be possible for someone to sneak in a fish into the area, though fish must be alive when registered to qualify for a prize. It would also be possible for a participant to sneak a fish into a hole the night before the competition.

Organizers plan to have additional security protocols next year, said Shane Meyer, the event’s chairman.

Only two other anglers have been investigated for cheating over the event’s 28 years, he said.

“In those two cases, one person took a required lie detector test and passed it, and the other person declined, which was his right. When he did, he forfeited his prize,” Meyer said.

The event has raised more than $3.3 million for charities since its founding.