Search and rescue efforts suspended for six people following Baltimore bridge collapse.

The US Coast Guard says it is suspending search and rescue efforts in Baltimore, after a cargo ship lost power and hit a bridge - causing it to collapse. State Police say the rescue mission has now changed to a recovery operation, to find the six people who are still missing. Two people were rescued, after they were thrown into the river. Al Jazeera’s Heidi Zhou-Castro is monitoring the latest developments near that collapsed bridge in Baltimore. Colin Caprani is a bridge engineering expert and head of structural engineering at Monash University. He explains why and how the bridge collapsed the way it did