VICKSBURG, Miss. — The Mississippi River remains closed at Vicksburg on Monday as authorities worked to determine whether a sunken barge was a navigation hazard.

Coast Guard Lt. Ryan Gomez says an assessment is underway but it is uncertain when the river will reopen to ship traffic.

Gomez says 233 barges are waiting to move northbound and 119 barges are waiting to move southbound.

The Coast Guard closed the river Sunday after the old U.S. Highway 80 railroad bridge was struck by barges that broke free from a string under tow.

About 30 barges broke free, and at least one sank. The Coast Guard says three others had been nudged against the river bank. The remaining barges had been rounded up.

The barges were believed to be carrying grain and coal.