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 started 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 Mayor William William Akers said there is no issue with potentially compromised wiring on the surviving sections of the boardwalk.

"We did a total rebuild. All 16 blocks got all new wiring," he said.

In Point Pleasant Beach, one of the approximately half-dozen Sandy-ravaged towns where businesses with electrical connections are located on the boardwalk, Mayor Vincent Barrella said streetlight wiring is all new in a section of the boardwalk that was rebuilt last winter.

But he said about half the boardwalk, including sections in front of businesses, still needs to be redone this winter. After the prosecutor issued his warning, Barrella said he instructed borough officials to work with the local electric company and identify any wiring that might need to be replaced as part of the upcoming work.

Investigators said the Seaside 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 arc that is believed to have started the fire. Coronato said those wires had been exposed to the storm surge and the 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."

Seaside Park pizzeria owner Angela Papoutsakis was worried by the findings.

Flames from the boardwalk fire caused only minor damage to George's Pizza, which she and her husband operate, but destroyed the building next door.

The couple had to have their wiring and sprinkler system re-inspected before they were allowed to open for the summer season.

"This makes me really nervous," she said. "We did what we had to do. And now we're wondering if they (town inspectors) did what they needed to do."

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 business affected by the fire postpone filing sales and use tax returns that were due this month until Oct. 21 to help them recover.

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Associated Press writer Samantha Henry in Seaside Park contributed to this report.

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Wayne Parry can be reached at http://twitter.com/WayneParryAC