Iceland lowered its aviation alert level to orange from red Sunday, saying there was no sign of an imminent eruption at the Bardarbunga volcano. And scientists at the Icelandic Meteorological Office said their announcement Saturday that the volcano had experienced a subglacial eruption was wrong.
But the office cautioned in a statement that seismic activity at the volcano, which has been hit by thousands of earthquakes over the past week, was not slowing, and an eruption remained a possibility in coming days.
Two earthquakes measuring over 5 in magnitude — the biggest yet — shook the volcano beneath Iceland's vast Vatnajokull glacier early Sunday. The Met Office recorded earthquakes of 5.3 and 5.1 in the early hours.
Iceland had raised the alert for aviation Saturday to red, the highest level on a five-point scale, warning that an ash-emitting eruption could be imminent.
An orange alert indicates "heightened or escalating unrest with increased potential of eruption."
After the alert was lowered, aviation authorities lifted a no-fly zone that had been imposed for 100 nautical miles by 140 nautical miles (185 kilometers by 260 kilometers) around the volcano.
A 2010 eruption of Iceland's Eyjafjallajokul volcano caused a week of international aviation chaos, with more than 100,000 flights cancelled. Aviation officials closed Europe's air space for five days out of fear that volcanic ash could harm jet engines.
Any new eruption would be likely to be less disruptive. European aviation authorities have changed their policy, giving airlines detailed information about the location and density of ash clouds but leaving decisions to airlines and national regulators.
"Even if there were to be a major eruption, it would not necessarily produce a high ash column, so the likelihood of interruption of trans-Atlantic and European air travel remains low," said Open University geoscientist David Rothery.
Britain's National Air Traffic Service said it was monitoring what it called a "dynamic situation" but was expecting normal operations Sunday.
Lawless contributed from London.