It's reported one passenger has a broken leg and the others were burned, though the full extent of their injuries is not known at this time.
He didn't observe 'any major explosions, ' so he navigated his vessel closer, to about 250 yards away from the lava.
He said that the crew didn't pick up on any warning signs before the explosion.
An explosion sent a "lava bomb" crashing through the roof of a tour boat off Hawaii's Big Island, injuring 23 people Monday, officials said.
The boat was off the island's Eastern coast on Monday morning when the volcano sent what officials said was a basketball-sized "lava bomb" through the boat's roof and peppered it with volcanic debris. "Just really good people".
'What I saw in humanity this morning was incredible. We expect a high rate of earthquakes (25-35 per hour) to continue until the next collapse/explosion event occurs later today. A woman who answered the phone at Lava Ocean Tours confirmed that it was the company's boat that suffered the explosion but declined to comment further.
Officials have warned of the dangers of toxic fumes, created when molten rock hits the sea and forms hazardous clouds containing hydrochloric acid and glass particles. The Coast Guard said tour vessels have operated in the area going back at least 20 years.
It has destroyed more than 700 homes since then.
Kilauea Volcano pictured in June.
The observatory added that the tiny island is likely part of the flow from fissure number eight, which is entering the ocean.
But until now there had only been one serious injury, a man whose leg was hit by a projectile of molten rock as he sat on a balcony.
"[Four] passengers taken by ambulance to the hospital, one seriously injured with a fractured femur".