ANCHORAGE, Alaska (AP) - Geologists monitoring Mount Redoubt for signs of a possible eruption noticed that a hole in the glacier clinging to the north side of the volcano had doubled in size overnight - and now spans the length of two football fields.

Scientists with the Alaska Volcano Observatory on Friday flew close to Drift Glacier and spotted vigorous steam emitted from a hole on the mountain. By Saturday, they had confirmed the area was a fumarole, an opening in the earth that emits gases and steam, that was increasing in size at an alarming rate.

They also saw water streaming down the glacier, indicating heat from magma is reaching higher elevations of the mountain.

"The glacier is sort of falling apart in the upper part," research geologist Kristi Wallace said.

The signs of heat add to concerns that an eruption is near, which could send an ash cloud about 100 miles northeast toward Anchorage, the state's largest city, or onto communities on the Kenai Peninsula, which is even closer to the mountain on the west side of Cook Inlet. It would be the first eruption since 1990.