Baltimore's collapsed bridge has brought the country's ninth-biggest foreign trading port to a standstill with 10 ships trapped inside.

The Francis Scott Key Bridge was knocked over when Singaporean container ship Dali crashed into one of the support columns about 1.30am on Tuesday. Baltimore handled 52.3 million tons of foreign cargo last year worth about $80.8 billion, ranking ninth in the US for both metrics and records for the port.