Kilauea Volcano has started erupting within Halemaumau Crater, U.S. Geological Survey officials said, and droves of people are already making their way to see the lava flow.

USGS’ Hawaiian Volcano Observatory said scientists detected a glow in Kilauea summit webcam images at 4:44 a.m. Wednesday, “indicating that an eruption has commenced within Halemaumau crater in Kilauea’s summit caldera, within Hawai‘i Volcanoes National Park.”

“The opening phases of eruptions are dynamic,” an HVO statement said. “Webcam imagery shows fissures at the base of Halemaumau crater generating lava flows on the surface of the crater floor. The activity is confined to Halemaumau and the hazards will be reassessed as the eruption progresses.”

As of late Wednesday afternoon there were “multiple minor fountains” on the crater floor, HVO said. While the height of the fountains had shrunk since the beginning of the eruption, they were still between about 13 to 30 feet high at the time of the report.

The lava flow added about 30 feet of new lava to the crater floor.

HVO has elevated Kilauea’s alert level from “watch” to “warning” and its aviation color code from “orange” to “red.”

The volcanic activity is confined entirely within the park, officials said.

“The lava this morning is all confined within … the summit caldera. So plenty of room for it still to produce more without threatening any homes or infrastructure,” said park spokesperson Jessica Ferracane. “So that’s the way we like our eruptions here.”

The park is already packed with people who want to see the lava flow.

“I can tell you it is extraordinarily busy. We’ve had full parking lots, pretty crowded overlooks,” Ferracane said. “The word is definitely out that the volcano is erupting again.”

Since the park is open 24 hours a day, visitors can beat the crowds by visiting between 9 p.m. and sunrise.

“It is a super spectacular eruption. It is quite beautiful. We have a 371-acre lava lake in the middle of the crater that people can see from many vantage points along Crater Rim Trail,” she said. “It is definitely going to draw many, many more thousands of visitors over the next couple of days and definitely through the weekend.”

Hawaii County Civil Defense officials said there is no volcanic threat to any community. “Due to the eruption, you can expect higher levels of volcanic gases and fine ash near the eruption site. Please take necessary precautions when near these areas,” they said in a community alert.

“Communities in the Puna, Kau and South Kona Districts may be affected,” National Weather Service officials said in a special weather statement. “Avoid excessive exposure to ash which is an eye and respiratory irritant. Those with respiratory sensitivities should take extra precaution to minimize exposure.”

The USGS also recorded dozens of small earthquakes in the summit region Wednesday with the largest at magnitude 3.4.

Kilauea is one of the world’s most active volcanoes. Its previous eruption, which also was confined to the summit caldera, ended March 7 after two months. For about two weeks in December, both Kilauea and Mauna Loa were erupting simultaneously, a rare event that threatened no residents or property but spurred a surge in tourism for Hawaii island.

Last month, Big Island residents marked the fifth anniversary of the start of Kilauea’s devastating Leilani Estates eruption which destroyed about 700 homes and structures, and caused hundreds of millions of dollars in damage.

Ferracane reminded visitors to stay out of closed areas and remain on marked trails for safety reasons, including avoiding gases from the eruption.

The National Park Serv­ice has provided notes for safe viewing for visitors, including staying on trails and overlooks and avoiding cliff edges and earth cracks; hazardous volcanic gases are dangerous to everyone, but especially people with heart or respiratory problems, infants and young children, and pregnant women; and the summit of Kilauea, which is at an elevation of around 4,000 feet, can be chilly, so rain jackets, long pants and closed-toe shoes could be helpful.

NPS is also reminding the public to drive slowly and expect long waits for parking spaces at popular vantage points like Kilauea Overlook and Devastation Trail parking lots.

The Associated Press contributed to this report.