Honolulu - An explosion sent lava flying through the roof of a tour boat off Hawaii’s Big Island, injuring at least 13 people Monday, officials said.

A 20-year-old woman suffered major leg trauma, and other passengers had burns and scrapes, the state Department of Land and Natural Resources said.

The people were aboard a tour boat that takes visitors to see lava plunging into the ocean from a volcano that has been erupting for two months. Several companies operate such tours.

Officials have warned of the danger of getting close to lava entering the ocean, saying the interaction can create clouds of acid and fine glass.

The U.S. Coast Guard in May instituted a safety zone where lava flows the ocean off the Big Island. It prohibits vessels from getting closer than 984 feet (300 meters) from ocean-entry points.

The agency allows experienced boat operators to apply for a special license to get up to 164 feet (50 meters) from where lava sizzles into the sea.

The molten rock is coming from the Kilauea volcano, which has been erupting from a rural residential area since early May and has destroyed more than 700 homes. But until now, the only serious injury was to a man who was hit by flying lava that broke his leg.

Officials were interviewing injured passengers at a hospital.