Mount St. Helens rumbled to life early Monday, shaking violently and spewing ash to a height of 30,000 feet.

Scientists could not make direct visual observation of the event because it occurred during darkness but said it was comparable to a minor eruption last winter.Chris Trisler, a spokeswoman at the University of Washington Geophysics Lab in Seattle, said seismographs monitoring seismic stations set up all around the volatile volcano began to fluctuate with an explosive-type signal at 2:07 a.m.

About eight minutes later, the Federal Aviation Administration said commercial pilots began reporting sighting a plume of ash at an altitude of 30,000 feet.

The volcanic event occurred without warning, Trisler said.