PORT CLYDE – A U.S. Coast Guard investigation was under way Friday into the sudden sinking two days earlier of the 50-foot fishing dragger Sirius that presumably took the life of its captain.

The Coast Guard’s search for Gary Thorbjornson of Port Clyde ended at 5:47 p.m. Thursday after search and rescue ships and aircraft had scoured 300 square nautical miles of ocean in the vicinity of Jeffreys Bank, some 30 miles off this peninsula town. The search had started at 9:30 p.m. Wednesday more than an hour after the dragger sank.

Family and friends relayed details Thursday indicating the Sirius had difficulty hailing the Coast Guard prior to the sinking, possibly due to poor radio reception.

Thorbjornson was groundfishing with one of the four fishing draggers in his father Edward Thorbjornson’s fleet when a rogue wave rolled the boat into the sea with three men on board. The captain’s son, Garrett, 17, and his friend, David Wilgus, 19, both of Port Clyde, plunged into the water, but managed to swim to a life raft. They last saw Gary Thorbjornson going below deck to retrieve survival suits. He did not resurface. Initial reports gave Gary Thorbjornson’s age as 40; but officials said Friday he was 42.

The Coast Guard has “no plans to resume a search at this time,” Ensign Ben Crowell, a Coast Guard spokesman, said Friday. Crowell said the nearest landfall from the sinking is about 25 miles.

On Thursday, relatives indicated the leaky wooden vessel was already having problems with its pumps not keeping up with intruding water. On Wednesday night, the crew members had hailed the fishing vessel Irene & Alton of Owls Head by cell phone when they realized they would have to abandon ship. Then the wave toppled the Sirius. Both younger men were rescued about an hour later by the captain of the Irene & Alton, Brad Hall of Thomaston.

On Friday, Lt. Daniel McLean, supervising officer of the Coast Guard’s marine safety field office in Belfast, said part of the investigation involves obtaining written statements and conducting interviews with the survivors and others involved with the vessel. He expects the investigation to be completed within a few weeks, but could not say when the findings would be released.

“Sirius is not a vessel required to be inspected by the Coast Guard,” McLean said, when asked about mandatory inspections. Commercial fishing vessels may have voluntary dockside inspections by the Coast Guard, he said, and are subject to random boarding at sea.

According to Crowell, the most recent boarding of Sirius by the Coast Guard was in July 2003 by Coast Guard personnel based in Rockland. The inspection found two discrepancies: the emergency position-indicating radio beacon, known as an EPIRB, had dead batteries and there was no guard on the vessel’s exhaust pipe.