Bonfires, an illegal ritual for teens and nighttime beach-goers, are increasing and have North Shore residents concerned for public safety and pleading for personal responsibility.

Beach bonfires spike during graduation season. But it's the popular use of wooden shipping pallets as a fuel source — typically with more than 60 nails in each pallet — that has Greg Gerstenberger calling for sensibility among fire builders.

Fires on the beach carry fines up to $500. But that hasn't stopped people from burning logs, brush and pallets for nighttime parties that can last for hours and include alcohol, which is also illegal on the beach.

The day after a bonfire party, the black pits left behind often continue to burn and are littered with broken beer bottles and cans that have been tossed into the debris, posing environmental and safety hazards.

Gerstenberger, who manages the vacation units at Ke Iki Beach Bungalows in Sunset Beach, said the number of bonfires have increased over the years, creating a danger for people who want to use the beach the next day.

"It's like the word is out," he said. "It's a great place to go and have a bonfire. On any given nice weekend, especially this last weekend because there was a full moon, you could go down to the beach and see three to five bonfires going on a 400-yard stretch."

The Sunset Beach Fire Station responded to 16 bonfires from March 1 to June 10.

"That's a lot," said Capt. Terry Seelig, spokesman for the Honolulu Fire Department. "We have noticed an increase in the number of bonfires."

Despite yearly pleas from the state and the posting of signs at beaches, illegal bonfires continue, said Deborah Ward, spokeswoman for the state Department of Land and Natural Resources, which has jurisdiction on beaches.

In recent years, two children have been burned when they inadvertently uncovered bonfires that had been covered with sand, a practice that only insulates the coals and keeps the fire smoldering, Ward said.

"DLNR does see fires, drinking and driving on the beach as public safety problems and potentially harmful to the environment," she said, adding that DLNR officers have cited and will respond to reports of fire along with police and the Fire Department.

Strong winds can blow embers that could ignite a home, Seelig said. The open fire itself also is dangerous to people around it who could fall in and get burned.

"Nails from pallets and components that are not totally consumed by the fire can become a hazard to people and a source of pollution to the beach," Seelig said.

Groups can obtain a permit to have a bonfire, but conditions include having an adult present, having water nearby to extinguish the blaze and calling fire officials just before lighting the fire, Seelig said.

Cooking fires such as imu are allowed as long as organizers also alert the Fire Department before lighting them, Seelig said. Other than an imu, all cooking fires on the beach are supposed to be in a container, like a hibachi.

The problem isn't limited to the North Shore. Kailua residents have complained for years, as well.

Rich Carvill, who lives near Kailua Beach, said in the past three weeks he's counted at least five bonfires.

Pallets are preferred, he said, and what's left behind are nails and glass and cans that were tossed into the fires.

"When you heat (nails) like that, they get real pointed," Carvill said. "It really makes for a lethal, rusty piece. Now you're into tetanus."

The latest bonfire at Kailua was a 5-foot-deep hole that was 10 feet across, he said.

Some parties start small but — when word gets around — as many as 60 people might show up, including teenagers who are obviously drinking, Carvill said. "They're getting in cars at 2, 3 o'clock in the morning and you can hear them taking off," Carvill said. "It's like if police want to catch drunken drivers, there they are."

Several bonfires have been averted when party planners brought their material to the beach early and stored it there, he said. Residents would remove the material, Carvill said, adding that communities should do that as a means of stopping the fires.