A volcano in western Indonesia that has been spewing clouds of searing gas high into the air has let out a new powerful burst.

Authorities say they are closely monitoring Mount Sinabung on Sumatra, one of Indonesia's main islands. It was placed at the highest alert level last week.

Government volcanologist Surono said hot ash tumbled down Sinabung's slopes up to 2.5 kilometers (1.5 miles) from its smoldering mouth on Wednesday. He is urging villagers to stay out of the main danger zone, which stretches 7 kilometers (4 miles) to the southeast of the crater. No injuries have been reported.

The volcano has been shooting smoke and ash more than 500 meters (1,640 feet) into the air since Monday.

Sinabung is among some 130 active volcanoes in Indonesia.