The Interstate 40 bridge over the Mississippi River has been closed after authorities said they found a crack in the span linking Arkansas and Tennessee. The Arkansas Department of Transportation tweeted on Tuesday that it found the crack during a routine inspection of the bridge. The department said it was working with the Tennessee Department of Transportation to assure the bridge is safe before reopening. Traffic was being rerouted to the Interstate 55 bridge over the river. It’s unclear how extensive the crack was or what caused it.