One of Iceland’s most feared volcanoes looks ready to erupt, with measurements indicating magma movement, Icelandic experts said Wednesday, raising fears of a new ash cloud halting flights over Europe.

The Hekla volcano is close to the ash-spewing Eyjafjoell, which last year caused the world’s biggest airspace shut down since World War II, affecting more than 100,000 flights and eight million passengers.

The Iceland Civil Protection Authority told AFP it was closely monitoring the situation.