At least 23 injured as 'lava bomb' hits tour boat near Hawaii's Kilauea volcano

The 'flying' lava punctured the boat's roof, leaving a gaping hole. At least 23 were injured by the lava. [AFP]

An explosion caused by lava oozing into the ocean sent a lump of molten rock crashing through the roof of a sightseeing boat off Hawaii’s Big Island, injuring 23 people.

A woman in her 20s was in serious condition with a broken thigh bone after being hit by the “lava bomb”, the Hawaii County Fire Department said.

Three others were in stable condition at a hospital with unspecified injuries. The rest of the passengers suffered burns, scrapes and other superficial injuries. 

They were aboard a tour boat that takes visitors to see lava plunging into the ocean from a long-erupting volcano that has been vigorously shooting molten rock from a new vent in the ground for the past two months.

The lava punctured the boat's roof, leaving a gaping hole, firefighters said. 

Shane Turpin, the owner and captain of the vessel that was hit, said he never saw the explosion that rained molten rocks down on top of his boat. 

He and his tour group had been in the area for about 20 minutes making passes of the ocean entry about 500 metres offshore, he said.

“As we were exiting the zone, all of a sudden everything around us exploded,” Mr Turpin added: “It was everywhere.”

Mr Turpin said he had no idea just how big the blast was until he saw video of the event later on shore. 

“It was immense,” he said. “I had no idea. We didn't see it.”

The captain has been navigating lava tour boats for many years and has lived on the Big Island since 1983.