Federal Aviation Administration officials are investigating an emergency landing of a tour helicopter near Hilo Airport on Thursday.

The Paradise Helicopters aircraft with a pilot and four passengers aboard was returning to the airport at about 1:15 p.m. after touring Kilauea Volcano when the pilot reported engine failure, authorities said.

The helicopter landed by auto-rotating to the ground, coming to rest on its side near the airport, authorities said.

There were no reported injuries, state transportation spokes­woman Caro­line Sluyter said.

"When the airport rescue and the firefighters arrived, the pilot and passengers had already evacuated the helicopter," Sluyter said.

FAA spokesman Ian Gregor said the helicopter was headed for Hilo when the pilot declared an engine failure.

Dustin Acdal, a freelance photographer who was at the scene, said the helicopter was damaged.

"It was resting on its right side. Two of the bent propellers were up in the air," Acdal said. "It looked like the back cover on the left side came off."

Rob Payesko, Paradise director of business, said company officials don’t know what caused the emergency landing. "We’ll have to wait and see," he said.

Payesko said damage to the helicopter was being assessed.

He said the McDonnell Doug­las aircraft had been on the tour for 40 to 45 minutes.

"We’re are thankful no one was injured," Payesko said.