Visitors are flocking to Hawai‘i Volcanoes National Park to watch as lava continues to fill Halemaumau Crater, but the crowds are causing some safety issues for park rangers, who are citing people wandering into closed and unstable areas.

The U.S. Geological Survey reported the crater lake to be 554 feet deep as of 7 a.m. Thursday morning — an increase of 39 feet in just 24 hours. The lake is being fed by two active vents in the crater, in the Kilauea caldera on Hawaii island.

Lava flow began Sunday night, and since then there has been a “sharp increase” in the number of visitors who want to watch the resulting plumes of gas and steam, according to a news release from the national park.

The eruption is contained in an area of Halemaumau that’s been closed since 2007, where there are “dangerous levels of volcanic gas, rockfalls, explosions and volcanic glass particulates.”

Park officials have been urging the public to use caution as thousands of visitors head to the volcano, and park rangers have cited dozens of people who venture into dangerous areas to take photos and videos.

“All it takes is a slight change in wind direction and these offenders could inhale a fatal dose of volcanic gas. One misstep or a crumbling cliff edge and they could plunge into the vast pit of molten rock or to the crater floor,” said Chief Ranger Jack Corrao in a statement. “We want to keep the park open so everyone can safely experience this beautiful new eruption, but when visitors enter closed areas, rangers must concentrate on these few individuals. This puts our staff in hazardous situations and causes them to shift their focus away from the safety of visitors experiencing the eruption in designated viewing areas.”

Penalties for violations of closures start at $150, according to Jessica Ferracane, spokeswoman for Hawai‘i Volcanoes National Park. The penalties increase with multiple violations and can lead to expulsion from the park.

There are designated viewing areas at the park that are open 24 hours per day, and include Waldron Ledge, Wahinekapu, Mauna Loa Lookout, Keanakakoi and Volcano House.

The eruption has also drawn more visitors who want to watch the lava from the sky.

At least one helicopter tour company, Paradise Helicopters, has noticed a substantial increase in bookings since the lava flow began, said Bronsten Kossow, the company’s operations manager, in an Associated Press story.

“The call volume is way up, and people want to fly now,” Kossow said. “The volcano immediately started the phones ringing. Everyone who is here wants to get up and fly.”

The company booked all of its aircraft and pilots and conducted nine flights Monday — figures the company has not reported since before the pandemic began.

Kossow said that before the pandemic the company flew about 30 to 40 flights per day.

The Federal Aviation Administration issued a temporary flight restriction Thursday, which restricts operations of certain aircraft above the volcano. The restriction is set at 9,000 feet above sea level with a 3-nautical-mile radius and will last through Monday.

Ferracane said USGS is flying to gather data and imagery to keep the public safe.

The USGS didn’t report any new significant changes in volcanic activity Thursday morning, but said the continuous release of volcanic gas that turns into volcanic smog can be a health hazard.