The Icelandic Meteorological Office reported intense earthquake swarms in the southwestern part of the country in recent weeks, likely tied to the movement of underground magma, or molten rock, in and around the Reykjanes Peninsula.
The sharp uptick in seismic activity prompted authorities to evacuate all 3,400 residents from the town of Grindavik on Saturday. The U.S. Embassy in Iceland, which issued its own volcano alert Friday, said seismic activity created ruptures on the primary road to Grindavik.
Iceland’s Civil Protection Agency warned that a large magma tunnel is forming that could reach the town. Volcanic eruptions occur when magma pushes up from the Earth’s crust, forming lava at the surface.
Officials said it's not yet clear if the magma will reach the surface — and where that may occur — but added that the evacuation was ordered with the safety of residents in mind. Still, authorities said that there is no imminent danger and that people should not panic.
"It’s important that everyone remain calm, because we have a good amount of time to react," the agency said in a statement issued late Friday.
The meteorological office is closely monitoring the situation and said Monday that around 900 earthquakes had been detected since midnight but that their size and intensity were decreasing. Earlier in the day, officials said ground deformation in the region has also slowed, which “can be an indication that magma is moving closer to the surface.”
The U.S. Embassy's alert followed the earthquake swarms and other signs of volcanic activity in the Reykjanes Peninsula.
Embassy officials said volcanic hazards may include lava, toxic gases and heavy smoke from fires ignited by lava.
Iceland is one of the most active volcano hot spots in the world, owing to the island’s location where two tectonic plates, the Eurasian and the North American plates, are slowly moving away from each other.
The movement along these plate boundaries frequently produces earthquakes, and as the planet's crust pulls apart, magma can rise to the surface, triggering volcanic eruptions.
There are around 30 active volcano systems in the country, according to the meteorological office.
In 2010, a series of major eruptions at the Eyjafjallajökull volcano in Iceland produced an enormous ash cloud that blanketed the area, causing extensive air travel cancellations across Europe.
This article was originally published on NBCNews.com