Two Lexington Park men out fishing on the Chesapeake Bay were killed Saturday morning when their boat took on water, then rolled on its side, authorities said.

David Chase, 55, and David Fletcher, 43, had set out from Point Lookout State Park in St. Mary’s County with four others for the first day of striped bass season when at about 9:30 a.m., their boat began taking on water, authorities said. The 23-foot vessel soon flipped on its side, stranding the six people on board in one of the widest portions of the Chesapeake Bay, said Maryland Natural Resources Police spokesman Brian Albert.

Rescuers pulled four people from the water with only minor injuries — the boat’s owner, his wife and their teenage son, along with Fletcher’s fiance — but Chase and Fletcher were killed, Albert said.

Albert said it remains unclear what caused the boat to take on water. He said there were waves of three to five feet in the area when the boat capsized, but investigators were not sure yet whether that or some mechanical problem was to blame for the incident. He said police believed the mishap was an accident involving only one boat.

“It can have some pretty treacherous water when the wind is blowing as hard as it is today,” Albert said.