A Hawaiian tour boat was hit by a lava bomb—lava. bomb.—on Monday morning, and at least 22 passengers were injured after at least one hunk of lava smashed a hole in the vessel’s roof, according to Hawaii's Department of Land and Natural Resources (DLNR). Most passengers had minor burns and one woman suffered a broken leg, according to the state agency. The boat’s railing was also damaged, local news site Big Island Now reports. Named ‘Hot Spot,’ the boat was operated by Lava Ocean Tours, which leads daily three-hour lava-spotting tours on small vessels that hold up to 49 people.

The explosion that launched the so-called lava bomb—an actual scientific term for molten lava more than two inches wide that hardens as it flies through the air.

Lava has been flowing constantly from Kilauea, the world's most active volcano, since May, causing evacuations and destroying homes in the Big Island's southeast corner. The eruptions have even created new, mini-islands on the southern coast. On land, most of the island's Volcanoes National Park is still closed because of continuous eruptions, while the U.S. Coast Guard has established a safety zone at sea that boats must steer clear of. The DLNR said on Facebook that the damaged boat was outside of the restricted zone when it was hit.