The 1730 m (5676 ft) high Cleveland Volcano, also known as Mount Cleveland, began erupting early on Tuesday,?and it?may be preparing for a more explosive event.

Cleveland Volcano has been in low-level eruption since the end of July, the Alaska Volcano Observatory said.

"An eruption for us is any time that magma is coming up from the surface in the ground," said John Power, scientist in charge at the observatory, a joint federal-state operation. "This is very much happening here."

Chuginadak Island is uninhabited and the volcano has not posed an immediate hazard to anyone or affected air traffic, even though it lies directly in the North America-to-Asia flight corridor used by major airlines, Power said.

But there is a possibility that the extrusion of lava is a precursor to a big explosive event that would send ash into the atmosphere, he said.

The dome, if it continues to grow, could plug up the crater, creating pressure that could result in "a fairly sizable explosion that could throw ash up to flight levels," Power said.

The Alaska Volcano Observatory first reported the eruption a week ago, when satellite images showed that the lava dome on the volcano's summit was widening.

Cleveland's last major eruption was in 2001, but it has had several smaller or suspected ash-spewing eruptions since then.