Disasters

Why did the I-35W bridge collapse?

Navy divers investigate site of the bridge collapse.
In this handout photo provided by the U.S. Navy, Navy divers from Mobile Diving and Salvage Unit (MDSU) 2 from Naval Amphibious Base Little Creek, Va., enter the water at the site of the I-35 bridge collapse over the Mississippi River on Aug. 7, 2007 in Minneapolis.
Joshua Adam Nuzzo | U.S. Navy via Getty Images 2007