ANCHORAGE, Alaska — A volcano in Alaska’s Aleutian Islands has sent up two more ash clouds but neither reached 20,000 feet, the height as which ash becomes a major concern for intercontinental air carrier flights.

The Alaska Volcano Observatory says Bogoslof (BOH-gohs-lawf) Volcano erupted at 11:23 a.m. Thursday and produced a cloud that reached 18,000 feet.

A second eruption at 12:35 p.m. sent up an ash cloud to 14,500 feet.

Both eruptions were seen by pilots.

Bogoslof is 850 miles southwest of Anchorage. The volcano has erupted more than 10 times since Dec. 16.

The observatory says more eruptions producing ash clouds, which can damage jet engines, could occur at any time with little warning.