Scientists are monitoring unusual underground activity that could signal an eruption at the Hekla volcano in southern Iceland.
University of Iceland geophysicist Pall Einarsson said Wednesday that magma appears to be moving deep beneath the volcano.
He says that does not necessarily mean an eruption is imminent.
But scientists expect Hekla, one of Iceland's most active volcanoes, to erupt soon.
In the past few decades, Hekla has erupted about every 10 years, most recently in February 2000.
Iceland, in the remote North Atlantic, is a volcanic hotspot.
In April 2010, ash from an eruption of its Eyjafjallajokul volcano grounded flights across Europe for days, disrupting travel for 10 million people.
In May, the Grimsvotn volcano erupted, causing minor disruption to air travel.