Debris from the first blast on Sunday mixed with moisture aloft, which later fell as a muddy rain on six nearby villages.
Officials rushed to distribute face masks to protect those downwind of the eruption from breathing in the ash.
Lokon is one of Indonesia’s most active volcanoes, but has produced an unusually high level of activity over the past few months. It has generated seven blasts since mid-September.
An eruption in July 2011 prompted the evacuation of more than 5,000 people. It has since spewed clouds of ash about 600 times, according to government vulcanologists.
The mountain is located just a few miles from the North Sulawesi provincial capital of Manado.
Previous eruptions have created fertile conditions that now support thriving businesses for those who grow coffee and cloves on Lokon's slopes.
But recent activity has prompted officials to establish a two-mile exclusion zone around the summit crater.
Photo: Volcanology Survey of Indonesia