Four foreign tourists and a local tour guide were killed early Tuesday morning when Mayon volcano erupted in the Philippines. A tour group comprising three tour guides and five foreigners were climbing the volcano when it erupted at approximately 8am. Tour guide Kenneth JeSalva later told a local TV news station that four of his group were killed when a rain of huge rocks "as bis as a living room" began falling on them. Reports said up to seven other climbers in other groups on the mountain were injured. The Philippine Institute of Volcanology and Seismology (Philvolcs) said in a press release later that the eruption was a phreatic eruption, when the magma heats ground or surface water, creating an explosion of steam, water, ash and rock. Such eruptions can occur with little or no warning. Philvolcs said that no volcanic eruption was imminent and the alert level remains at 0."