On Monday, a ball of molten rock struck a lava tour boat following an explosion caused by lava spraying out of the ocean just off the Big Island of Hawaii. As reported by CNN, 13 passengers were rushed to the hospital and another 10 had injuries that did not require hospital care. One women in her 20s ended up in critical condition with a fractured femur.

It is unclear where exactly the incident took place but it is an estimated one hour-long drive back to shore depending on waves. Upon return, a witness said that there were rocks all over the boat, and “some people leaving the boat had burns and gashes on their legs. One person was taken off on a stretcher.”

The boat reportedly holds 49 people, but it was unknown how many were on board.

According to the Associated Press the U.S. Coast Guard instituted a safety zone in May. It prohibits vessels from getting closer than 984 feet from ocean-entry points where the lava flows into the ocean. However, the agency allows experienced boat operators to apply for a special license to get up to 164 feet from where lava enters the sea.

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