The Alaska Volcano Observatory says pressure is building up once again after a blast last December cleared most of a lava dome that had been growing since October.
Cleveland lies beneath several major international air routes, and its ash plumes can force airlines to reroute flights to steer clear of potential danger to jet engines.
A second Aleutian volcano, Kanaga, has also started showing signs of increased activity, with tremors and small ash clouds being reported by observers. Kanaga lies just 16 miles west of the remote community of Adak.
Photo: Cyrus Read - Alaska Volcano Observatory