The massive fire that destroyed part of a Jersey shore boardwalk and dozens of businesses began accidentally in wiring damaged in Superstorm Sandy, and should prompt coastal property owners to inspect their own equipment for similar danger, officials said Tuesday.

The boardwalk fire in Seaside Park and Seaside Heights began accidentally Thursday in aged wiring that had been compromised by salt water and sand during the Oct. 29 storm, federal and county investigators said at a news conference. The wind-whipped blaze destroyed more than 50 businesses in the two towns.

Ocean County Prosecutor Joseph Coronato said the fire should be a cautionary tale.

“I’m sure on every boardwalk everywhere (at the Jersey shore), there may be compromised wiring,” he said. “We don’t want to start a panic mode. We just want to be reasonable. If you’re a property owner and you think your electrical work came in contact with water and sand, we strongly recommend you have it inspected.”

Seaside Heights officials did not immediately return a message seeking comment about the status of wiring in the surviving two-thirds of the boardwalk.

Investigators said the fire began in wiring that dated to the 1970s and was located under a frozen custard stand and candy shop.

Jessica Gotthold, a senior special agent with the Bureau of Alcohol, Tobacco, Firearms and Explosives, said investigators located wires under the boardwalk that somehow came in contact with each other, causing an electrical arc that is believed to have started the fire. Coronato said those wires had been exposed to the storm surge and grating sand action of the storm, which compromised them.

But as far as why the wires contacted each other, he said, “we will never know.”

The prosecutor said the investigation ruled out all other possible causes of the fire, including careless smoking or a deliberate act of arson. The wiring was inaccessible to the public, he noted.

Authorities even pulled financial records of the businesses involved in the blaze to make sure no one had a financial motive to start a fire.

“We left no stone unturned,” he said. “This was not a suspicious fire.”

It was only by destroying part of the 5-month-old boardwalk that Seaside Heights had just spent $8 million to rebuild that the rest of the walkway was saved. Public works crews ripped out a 25-foot swath of boardwalk to serve as a makeshift fire break, depriving the blaze of fuel. They then filled the void with giant sand piles — makeshift dunes to hold back fire, not water.

The desperation plan worked and stopped the fire from burning the rest of the boardwalk.

Gov. Chris Christie’s administration decided the state will use Sandy-recovery money to pay for debris removal. He also pledged $15 million in Sandy money to help rebuild the burned businesses.

Christie said Tuesday the state will let businesses affected by the fire postpone filing sales and use tax returns that were due this month until Oct. 21 to help them recover.