Updated 01/12/12 – 11:14 a.m.

SENECA, Ill. (CBS) — Damage could be as much as $2 million from a fire at a boat storage facility in LaSalle County.

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The fire broke out early Thursday on the decks of at more than 20 yachts at the Spring Brook Marina, along the Illinois River in the town of Seneca, about 75 miles southwest of downtown Chicago.

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Around 2 a.m., a Seneca police officer on patrol noticed smoke coming from the marina.

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Seneca Fire Chief Jerry Sears said that, within minutes, the flames spread from one boat to another, until 15 were destroyed. A half dozen others were damaged.

“They’re burned down to nothing. You can’t even tell they were boats,” Sears said.

Although no cause had yet been determined as of Thursday morning, Sears said it appeared suspicious.

“They’ve been wrapped up in plastic since October, probably, and there really wasn’t a reason for them to catch fire,” he said.

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The boats all belonged to private owners who were storing them at the marina for the winter.