Description:Scientists in New Zealand warned on Thursday (Nov 22) that Mount Tongariro could erupt again without warning after the volcano sent a plume of ash four kilometres into the sky a day earlier. Volcanologists said the risk of another sudden blast within days was significant. Local media said last week temperatures were reported to be rising hundreds of metres beneath the volcano, and there was an increased chance of an eruption. No injuries were reported from the eruption.(0:30)