REYKJAVIK, Iceland, May 6 (UPI) -- Iceland's volcano roared back to life Thursday, shooting a plume of ash 4 1/2 miles high and appearing ready to blow again, Iceland's meteorology office said.
"The eruption has changed back to an explosive eruption, lava has stopped flowing and most of the magma gets scattered due to explosions in the crater," the Icelandic Meteorological Office and the Institute of Earth Sciences at the University of Iceland said in a statement.
"The ash plume rises high above the crater (2 1/2 to 4 1/2 miles) and considerable ash fall can be expected in wind direction," the statement said. "No signs of the eruption ending soon."
The statement came as authorities started rerouting trans-Atlantic flights and the Irish Aviation Authority announced six western Irish airports would be shut until at least 1 p.m. local time Friday due to a "massive ash cloud" 1,000 miles long and 700 miles wide drifting into the country's airspace.
The affected airports are Shannon, Donegal, Sligo, Ireland West (Knock), Galway and Kerry, the agency said.
British and Irish authorities had just reopened the skies to planes several hours earlier after shutting airports in Scotland, Ireland and Northern Ireland Tuesday and Wednesday.
Ash from Iceland's Eyjafjallajokull volcano, located beneath a glacier in southern Iceland, first forced authorities across Europe to ground an estimated 100,000 flights and 10 million passengers April 14-20 in the worst peacetime air travel disruption in history.
British Airways said Thursday its passenger numbers dropped by almost a quarter last month as a result of the volcano-related flight bans, which forced the carrier to ground its fleet for the first time in its history.