ANCHORAGE, Alaska — An explosion Tuesday morning rocked Alaska’s Cleveland Volcano but scientists have detected no ash cloud that could threaten jets crossing the Pacific Ocean.

Scientists as the Alaska Volcano Observatory recorded an explosion at the volcano 940 miles southwest of Anchorage in the Aleutian Islands.

U.S. Geological Survey geologist Kristi Wallace said a similar explosion was recorded in November. Ash may have been produced but likely stayed under 20,000 feet, she said.

“We see this quite often and we think that they are associated with some sort of ash production,” she said.

Clouds obscured the sky at 30,000 feet. The observatory detected no ash above the clouds.

The Federal Aviation Administration and the airline industry become concerned for trans-Pacific flights when an ash cloud has the potential to exceed 20,000 feet.

Alaska’s Redoubt Volcano blew on Dec. 15, 1989, and sent ash 150 miles away into the path of a KLM jet carrying 231 passengers. Its four engines flamed out. The jet dropped more than 2 miles, from 27,900 feet to 13,300 feet, before the crew restarted all engines and landed the plane safely at Anchorage.

Cleveland Volcano is within 5,675-foot Cleveland Mountain, a nearly symmetrical peak that looks like an inverted V.

Cleveland Volcano forms the western part of Chuginadak Island and is 45 miles west of tiny Nikolski and its 15 permanent residents on Umnak Island. In previous eruptions, the village was not threatened by as the plume dispersed in other directions.

The volcano experienced a significant eruption in February 2001. Three explosive events generated ash as high as 39,000 feet. The eruption also sent out lava and a hot avalanche that reached the ocean.

In the last 14 years, Cleveland Volcano has occasionally produced small lava flows and explosions with small ash clouds below 20,000 feet. The explosions have launched debris onto the slope of the cone and sometimes hot avalanches.