The National Park Service reported "elevated earthquake activity" beneath Kīlauea's summit at around 2 a.m. HST Monday morning. Thirty minutes later, the USGS Hawaiian Volcano Observatory spotted eruptive activity while observing webcams.

NPS is warning those hoping to see the eruption -- which can be viewed on USGS webcams -- that hazardous volcanic gases are billowing into the air and "present a danger to everyone."

"This one came on really fast," Ken Hon of the USGS told Nexstar's KHON. "What we saw was a swarm of earthquakes as a crack opened up and allowed magma to come from the magma chamber up to the surface."

A line of fissures was seen with lava fountains at the base of Halemaʻumaʻu. Initially the fountaining was reaching heights of 250 to 300 feet but have since stabilized to well over 100 feet.

The eruption has covered the whole of the old Halemaʻumaʻu crater floor.

The activity is confined to the summit caldera and threats will be reassessed as the activity progresses.

Kilauea last erupted in September with a series of short eruptions in a remote area of Hawaii Volcanoes National Park. Hours later, a third phase of eruptions began in the Nāpau Crater.