Around 1:27am (05:27 GMT) on Tuesday, a holder transport slammed into one of the points of support supporting the Francis Scott Key Bridge in the city on the East Coast of the United States.
Baltimore's 1.6-mile (2.57km) Francis Scott Key Bridge was worked out of steel and opened in 1977.
Ship-tracking data showed a Singapore-flagged container ship
The harbour is one of the busiest in the country and an important hub for shipping on the US east coast, especially in transporting road vehicles.
The contractors were on the bridge making concrete deck repairs at the time of the collapse, and six remain unaccounted for.