Yesterday (21.04.2012) an earthquake swarm started in Hengill volcano at 18:57 UTC on 21.04.2012. The area in question is well known for having earthquakes swarms during past few months. It seems that this earthquake swarm is not over, and there is also a risk of stronger earthquakes in Hengill volcano than have currently happened. But the largest earthquake so far was event with the magnitude ML2.8.
Icelandic news about this earthquake swarm.
Jörð skelfur við Hellisheiðarvirkjun (mbl.is, Icelandic)