GRAND ISLE, La. (AP) _ A helicopter delivering workers to an offshore oil derrick barge flipped over Sunday, killing two men and injuring five others, authorities said.

A U.S. Coast Guard spokesman, Petty Officer Chuck Kalmbach, said three of its helicopters were searching the Gulf of Mexico for a missing eighth man, who like the two dead workers is an employee of McDermott Inc.'s marine construction division, based in Morgan City.

Dave Smith, vice president of operations for Air Logistics Helicopters in Lafayette, which ran the helicopter service, said it was not clear exactly what happened. He said the accident occurred after the Sikorsky helicopter had landed on the barge about 30 miles south of Grand Isle.

''It toppled during the process of disembarking passengers. It had aleady landed, but its (rotor) blades apparently struck the side,'' Smith said.

Officials said there were 45 mph winds when the accident happened at 8 a.m.

Smith said the chopper's two crew members were among the injured.

Ken Salzer, a spokesman for McDermott, identified the dead workers as Richard Seward, 43, of Gretna and Billy R. Jones, 36, of Algiers, La. He identified the missing man as Johhny P. Williams, 27, of Clovis, N.M.

Chuck Olivier, administrator at the Southeastern Louisiana Medical Center, said two men were admitted, one with a broken pelvis and another with cuts and scrapes. He said three others were treated and released.