By Nathalie Craig18 Jul 2018An investigation is underway after a “lava bomb” sent a molten lava shower down on the roof of a Lava Ocean Tours vessel off Big Island, Hawaii, injuring 23 passengers on board.A molten rock the size of a basketball smashed the metal roof of the boat while it was on lava tour off the coast of the Big Island yesterday.The Hawaii County Fire Department confirmed four people were transported to the Hilo Medical Center by ambulance while nine others went to the hospital in private vehicles and ten were treated on the scene for minor soft tissue injuries and burns.The most serious injury was a traumatic leg injury suffered by a 20-year old woman. All other passengers who went to the hospital were treated for minor scrapes and burns.Passengers on another nearby tour boat captured the explosion in the video below.DOCARE and the US Coast Guard are investigating the incident and have no further comment on what happened at this stage.It can be confirmed that the owner of the boat involved had a valid permit to be in the active ocean entry at Kapoho and also had permission to use the Wailoa harbor as its base of operation.“Clearly everyone is interested to learn what happened this morning. In the meantime, all of those injured today are very much in our thoughts for speedy and full recoveries.”State of Hawaii’s Department of Land and Natural Resources Chair Suzanne CaseThe explosion was part of the ongoing eruptions of the Kilauea Volcano that started in early May, causing destruction around the island.READ: HAWAII VOLCANO: Tourists are not affected & residents are being kept safeREAD: HAWAII UPDATE: No need to change travel plans, here’s what you can still doAre any of your clients on Big Island at the moment? Let us know below. Other stories you may likeHOORAY US-YAY: Book a cruise to the States and take home $100!START THE GROUP CHAT: $199 flights to Hawaii are hereTROPIC LIKE IT’S HOT: Free drinks and free wifi on your next NCL Hawaii cruise!