A fire of unknown origin Monday afternoon destroyed a historic covered bridge in the southern Aroostook County town of Littleton.

The Littleton Fire Department responded to the 110-year-old Watson Settlement Bridge on the Framingham Road (also known as Carson Road). Officials said two people driving by the bridge smelled smoke and spotted the flames after they turned around to investigate.

The 170-foot long wooden bridge was engulfed in flames when firefighters arrived. Crews from Monticello and Houlton assisted the Littleton Fire Department at the scene for several hours. The structure was severely damaged in the blaze, leaving only the charred trusses and partial framework.

The Maine State Fire Marshal's Office is investigating to determine the cause of the fire.

The Watson Settlement Bridge, which spans the Meduxnekeag River in southeast Littleton, was built in 1911 and was named for the Watson homestead that once stood nearby. It was one of just nine preserved covered bridges in Maine, and the only one in Aroostook County.

Although the youngest of the surviving Maine covered bridges, the Watson Settlement Bridge was the oldest example of the Howe Truss system. It was first listed in the National Register of Historic Places in 1970.

The bridge was closed to vehicle traffic in 1984 and has been accessible only by foot since then. It underwent a major restoration in 2015.

The remaining covered bridges in Maine are: Bennett Bridge in Errol, Lovejoy Bridge in Andover, Lowes Bridge in Guilford, Robyville Bridge in Corinth, Babb's Bridge in Gorham, Hemlock Bridge in Fryeburg, Sunday River Bridge in Newry and the Parsonsfield-Porter Bridge in Parsonsfield, Maine.

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