ANCHORAGE (AP) - The Alaska Volcano Observatory is keeping watch on a remote volcano that's showing signs of erupting.
The observatory Monday increased the alert level from "advisory" to "watch" at Semisopochnoi in the Aleutian Islands.
The volcano is on an uninhabited island between Attu and Adak near the west end of the Aleutian chain.
The observatory detected elevated seismicity Sunday. Activity at Semisopochnoi intensified Monday afternoon.
Tremor signals suggest that the volcano may have emitted ash or could soon. No eruption has been detected in satellite, lightning or infrasound data.
Ash sent above 20,000 feet (6,100 meters) can threaten airliner flights between Asia and North America.