BROOKSBURG, Ind. — Authorities in southern Indiana are trying to determine who’s responsible for damage to a 55-foot iron truss bridge near the Ohio River.

The single-span bridge near the town of Brooksburg about 10 miles east of Madison was immediately closed to traffic when the damage was found last Wednesday.

Jefferson County engineer Jim Olson said Monday the bridge’s closure means a 3- to 4-mile detour for area motorists. He says historic iron trusses that are part of the 80- to 90-year-old bridge weren’t damaged.

But a certified bridge inspector found that steel I-beams in the span had been overloaded and overstressed by a vehicle or vehicles well in excess of its posted 10-ton weight limit.

The inspector also says the bridge’s overloading was likely intentional since cedar support beams had been placed beneath it before the heavy load or loads were moved across.