Alert level raised on Alaska volcano

FILE: Eruption of Cleveland Volcano
ALASKA - MAY 23: (FILE PHOTO) In this photo provided by NASA, The eruption of the Cleveland Volcano is seen as photographed by an Expedition 13 crewmember on the International Space Station May 23, 2009 in the Aleutian Islands, Alaska. The Cleveland Volcano has erupted again yesterday sending a cloud of ash 15,000 feet into the sky according to reports on December 30, 2011. (Photo by NASA via Getty Images) (Getty Images)

The warning level for a remote Alaska volcano has been raised after a new lava dome began forming, indicating the mountain could explode and send up an ash cloud that could threaten aircraft.