Police are seeking witnesses to a fight that left a man in critical condition at Heeia Kea Pier on Monday night.

Police responding to a report of a large fight found an unresponsive man with head injuries near the boat launch area. The man was taken to a hospital in critical condition with head and brain injuries.

Police said someone punched the victim, a man in his 20s, who fell down and hit his head on the asphalt, police said.

The case is being investigated as a second-degree assault.

The pier is busy on holidays with people loading and unloading boats for trips to the Ahu o Laka sandbar in Kaneohe Bay. The state Department of Land and Natural Resources estimates that there were more than 200 boats and 500 people on the sandbar on Memorial Day Monday.

The state has stepped up enforcement and patrols on holiday weekends in Kaneohe Bay since a large brawl on Labor Day in 2007.