The Alaska Volcano Observatory has raised the alert level for Kanaga Volcano in the remote Aleutian Islands.

Scientists on Saturday said possible explosive activity and a likely ash cloud indicate new unrest at the volcano, leading it to raise the volcano alert level from normal to advisory.

The observatory says volcanic tremor was detected at about 6:23 a.m. Saturday. The unrest indicates a possibility for sudden explosions of ash to occur at any time, and ash clouds exceeding 20,000 feet above sea level may develop.

Ash clouds above 20,000 feet from Alaska volcanoes are a threat to trans-Pacific air carriers.

Kanaga Volcano is located about 1,215 miles southwest of Anchorage in the western Aleutian Islands.