(AP) - Seismologists say a year-long swarm of earthquakes in northwest Nevada could be linked to volcanic activity.
The University of Nevada's Reno Nevada Seismological Laboratory announced Tuesday that there have been 5,610 earthquakes in the swarm that started in July 2014 in the Sheldon National Wildlife Refuge near the Oregon border.
More than 200 have registered at a magnitude of 3 or greater, which is enough to be felt by the ranchers and residents nearby.
The largest one hit on Nov. 6 with a magnitude of 4.7, although there's also been a recent flare-up since mid-July.
Officials say volcanic activity can't be ruled out but there hasn't been direct evidence connecting it.
Nevada is the third most seismically active state in the country, behind California and Alaska.