ANCHORAGE, Alaska — An Alaska volcano that has been active for nearly six months has erupted again.

The Alaska Volcano Observatory says Bogoslof (BOH-gohs-lawf) Volcano in the Aleutian Islands erupted at 2:16 p.m. Sunday and sent a cloud of ash at least 35,000 feet (10,668 metres) high. The eruption lasted 55 minutes.

Ash can harm and stop jet engines. Ash from southwest Alaska volcanos is a threat airliners operating between North America and Asia when a cloud rises above 20,000 feet (6,096 metres).

After the eruption, the Aviation Color Code was raised to red, the highest level. It has since been downgraded to orange according to CNN.

The agency says a person on nearby Unalaska Island reports seeing a large white-grey mushroom cloud form over Bogoslof, with ash falling out to the west.