VINCENNES, Ind. — A project to restore a historic southwestern Indiana bridge will resume in October following a months-long delay caused by the discovery that endangered bats use the span as a roosting site.

The $3.2 million upgrade of the Lincoln Memorial Bridge that links Vincennes and Westport, Illinois, over the Wabash River was supposed to begin in March.

But crews found that the federal endangered Indiana bat uses the bridge as a roosting site and federal rules restrict work that could potentially disturb the bats between April 1 and Oct. 1.

A contractor will now begin work in early October for the expected six-month project that includes cleaning, paving and repairing the bridge’s facade.

The bridge was built in 1931 to compliment the George Rogers Clark National Park in Vincennes.