 PHIVOLCS noted in a March 22, 2001 report that since January 2001, earthquake clusters or occurrences had been recorded by the seismic monitoring network around the volcano.These earthquakes might had signified a reactivation of the volcanic system at depth and could be a precursor to more vigorous activity, such as ash explosions.This interpretation was based on similar earthquake clusters manifested prior to the August 10, 1996 phreatic explosion from the active summit crater of the volcano.