The Alaska Volcano Observatory has issued its highest level of alert for aviation after what it says was a brief eruption of a volcano on the Aleutian Islands.
The observatory said pilots reported the Bogoslof volcano on Bogoslof Island erupted about 4:00pm Alaska time.
The Aleutian Islands are a chain of volcanic islands in the Bering Sea, belonging to both the United States and Russia.
The pilots told the observatory that a volcanic ash cloud rose to 34,000 feet.
A red alert was issued, which the observatory defines as a hazardous eruption being imminent, underway or suspected.
The observatory said that satellite data show a short-lived explosion just before 4:00pm local time that drifted to the south about 15 minutes later.
The observatory said a subsequent pilot report at 4:50pm local time said the volcanic activity had decreased.