A rising, steaming lava dome grew at a faster rate yesterday inside the crater of Mount St. Helens, prompting scientists to predict a dome-building eruption within two days.

The Federal Emergency Management Agency in Vancouver said 35 to 40 shallow earthquakes a day continued to rattle under the mountain. The seismic level of the quakes remains moderate.

"Basically what we're doing is just waiting," said Christina Boyko of the University of Washington Geophysics Department. "We still think an eruption is likely by Saturday, maybe Saturday morning."

Clear skies afforded a look at a steam plume that rises 1,000 feet above the growing lava dome, a mound of hardened lava that may become the new summit for the peak.

A field crew of U.S. Geological Survey scientists returned to the floor of the crater for more tests on the mountain.

The USGS and the university issued an eruption alert last week, predicting that the volcano would erupt within three weeks.

When seismic activity increased last weekend, the scientists amended the alert, saying they expect an eruption within one to five days.

All indications point to another mild dome-building eruption, rather than an explosive blast like those that rocked the volcano six times in 1980.