HONOLULU ? Glowing lava set trees afire and oozed into the ocean before dawn Saturday as thousands of spectators braved Kilauea Volcano’s scalding spray to witness the spectacle.

It is the most dangerous display of volcanic activity from Kilauea since 1995. Since the flow began May 12, the lava has triggered one major fire, burning more than 3,600 acres.

The Hawaii Volcano Observatory reported that Saturday’s breakout of lava crossed the Chain of Craters Road and cascaded into the sea on the east side of the Big Island.

Although Kilauea has been erupting for nearly 19 years, officials say up to 2,500 people a day have been flocking to witness the latest dramatics.

“Conditions change rapidly,” said James Gale, a guide for Volcano National Park. “It’s really very powerful to see something like this face-to-face.”

Flights to Hilo International Airport are heavily booked and car rental agencies on the Big Island report having few vehicles. Park rangers say cars stationed along the road a few hundred yards from the flow have been backed up for two miles.

Rangers have warned visitors that the volcano can be deadly as the lava creates acidic and potentially harmful steam plumes and undermines the lava crust that can suddenly collapse.

In November 2000, two hikers died after they apparently were overcome by fumes where the lava enters the sea. In October, a woman fell to her death in Kilauea’s caldera.

Smoke from burning asphalt as lava meets road poses an additional danger.

“Delighted visitors are sucking up the asphalt smoke,” said Saturday’s early-morning report from scientists monitoring the flow.

Rangers hand out cotton gloves to protect against burns and have been using reflectors to mark the safest path to view the fiery show after dark.

Scientists from the U.S. Geological Survey’s Hawaiian Volcano Observatory reported seeing a pre-dawn glow Saturday from fires above the lava flow that “testifies to its presence in the forest.”

No buildings or major roadways have been threatened by the latest phase in Kilauea’s long eruption.

A Global Positions Satellite system is closely monitoring the broader rise of the lava, which could signal explosive activity. Tiltmeters placed on the lava show whether a dome is rising. A brief “inflammatory bump” was recorded on Friday but was flat by midnight and remained flat Saturday morning, the scientists said.

Seismic activity began increasing in the area in June with a “fairly high level” of earthquake activity, the scientists reported.