Quito, Ecuador ? Rescuers on Friday searched for 30 people missing after the devastating explosion of a volcano killed at least one person and forced tens of thousands to flee. The volcano appeared poised for a new eruption.

Ecuador’s Geophysics Institute urged residents and tourists who may be tempted to witness the spectacle to stay away from the 16,575-foot Tungurahua volcano in the nation’s central Andes.

The volcano is now quiet, but geology professor Theofilos Toulkeridis of Quito’s San Francisco University warned: “It is not good news that the volcano is calm. That is not a good sign.”

If Tungurahua remained plugged up “at the upper part of the chimney” it would start to “accumulate gas and magma,” he said. “The more time that passes with it capped, the worse it is.”

Volcanic ash rained down about 140 miles west of Tungurahua, which exploded before dawn Thursday and smothered its lush green slopes in a dull gray blanket of ash.