Tourists were seen walking inside the rim of the White Island crater just moments before the eruption.Police said 23 people had been rescued, but warned the number of dead was "likely" to rise. The area is currently too dangerous for a rescue operation.White Island, also known as Whakaari, is one of the country's most active volcanoes.Despite that, the privately-owned island is a tourist destination with frequent day tours and scenic flights available.