Kilauea has been rumbling today within Hawaiʻi Volcanoes National Park, prompting scientific observers to raise their alert level one step to “watch” from “advisory.”

The U.S. Geological Survey’s Hawaiian Volcano Observatory described the activity in an announcement this morning and emphasized that Kilauea is not erupting.

However, a swarm of earthquakes suggests that magma may be moving beneath the south part of Kilauea caldera, HVO said.

HVO reported that a swarm of earthquakes began Monday evening and continued with a “particularly strong sequence” of tremblers at about 1:30 a.m. this morning.

As of 4:30 a.m., over 140 earthquakes have been recorded, according to HVO, which said the largest one recorded had a 3.3 magnitude while most were under magnitude 1.

At about 6 a.m., HVO said small earthquakes were continuing at a rate of at least 10 per hour.

The ground-shaking activity, which was coincident with a change in the style of ground deformation at tiltmeters in Kilauea’s summit region, may indicate an intrusion of magma occurring 0.6 miles to 1.2 miles beneath the south caldera, HVO said.

“Currently, webcams and satellite imagery show no evidence of lava at the surface,” the report said. “HVO scientists will continue to monitor the situation and will issue additional messages and alert level changes as warranted by changing activity.”