A Philippines volcano has spewed a column of ash nearly 1.5 kilometres high into the sky, raising fears of a major eruption. Officials say they are considering increasing the alert level after Mount Bulusan in the central Philippines belched ash an hour before midnight local time. The Philippine Institute of Seismology and Vulcanology (Phivolcs) says the ash is unlikely to cause any harm. But researcher Jojo Cordon says more earthquakes have been recorded in the area recently, a possible sign the volcano may be about to erupt more powerfully. He says the ash column may have been created by a reaction between water and hot materials, a "possible sign of rising magma". A four-kilometre exclusion zone is already in place around the 1,565-metre volcano, which is 600 kilometres south-east of Manila. Phivolcs is considering raising the alert level for Bulusan from level one to level three, indicating "moderate unrest". The highest alert level is level five, indicating an actual eruption of lava.