Vandals at some Oahu beach parks have a new target: the large batteries that power many of the emergency sirens that warn residents of hurricanes, tsunamis and other disasters.

Since April, thieves have stolen siren batteries five times at beach parks, including three times at Haleiwa Beach Park, the city said Tuesday.

It’s a relatively new crime and one that affects public safety, said Peter Hirai, deputy director of the city Emergency Management Department.

"We want the public to be vigilant and report vandalism because these sirens protect them," Hirai said. "Nothing is more dangerous than a hurricane or tsunami approaching with the sirens not functioning."

The department is asking for the public’s help in monitoring the sirens and reporting suspicious activity to police.

Benjamin Bremer was with his family at Haleiwa Beach Park Tuesday. "It’s sad that people would steal from something that is meant to protect them," said Bremer, a Schofield Barracks soldier who says he enjoys barbecues with his family and friends at Haleiwa Beach Park.

Roughly half of Oahu’s 174 emergency sirens are powered on the grid. But newer models are solar-powered, with photovoltaic cells that charge batteries by day.

The city said each of the five thefts cost the city $400 to $600 to replace the batteries. Some sirens use two batteries; some use four. Hirai said they are wet-cell batteries, similar to a car battery, and weigh about 20 pounds each.

To combat the recent thefts, the park facilities crew installed a metal plate on the battery box to shield the padlock at the Haleiwa Beach Park, but it has not completely stopped the thefts, Hirai reports. Officials are thinking of other ways to protect the sirens, he said.

Hirai said that every month about 10 sirens are inoperable due to battery problems or other technical issues. Tests of the sirens are done monthly to determine which sirens need fixing.