A "lava bomb" struck a tour boat Monday morning in Hawaii, injuring 23 people.
The basketball-sized piece of lava reportedly burst from the water near the boat and landed on its roof.
The Hilo Medical Center confirmed 13 passengers were treated at the hospital, and another 10 passengers with superficial injuries were treated on arrival at Wailoa Harbor, CNN reported.
A woman in her 20s was in serious condition with a broken thigh bone. Three others were in stable condition, reports said, and the rest of the passengers suffered burns and scrapes.
A gaping hole could be seen in the boat’s roof after it returned to Wailoa Harbor, the Hawaii County fire department said. A railing was also damaged.
The incident took place about 500 yards offshore, the Guardian reported.
"As we were exiting the zone, all of a sudden everything around us exploded,” Shane Turpin, who owned the ship, told InsideEdition.com. "It was everywhere."
Turpin said he had no idea how big the blast was until he later saw a video of the moment.
Hawaii's Kilauea volcano erupted in early May and was still erupting lava as of Sunday.