Baltimore bridge collapse: NTSB releases images, video of investigators onboard stricken cargo ship

The National Transportation Safety Board (NTSB) has released images and video of its investigators onboard the stricken Dali cargo ship that remains stuck Thursday underneath the remains of the collapsed Francis Scott Key Bridge in Baltimore. 

Photos show NTSB investigators in hard hats launching drones and looking over materials on the bridge of the ship.  

"The real critical thing here is that, as you know, a portion of the bridge remains on the bow on that ship, and we will be coordinating very closely with the Army Corps of Engineers and their contractors to first effect the removal of that debris before the vessel can then be removed," Coast Guard Vice Adm. Peter Gautier said Wednesday. "The vessel bow is sitting on the bottom because of the weight of that bridge debris on there."  

At another press conference on Wednesday, NTSB chair Jennifer Homendy said the Singaporean-flagged cargo ship had been carrying 56 containers of hazardous materials, including corrosive flammable cells, lithium-ion batteries and other hazardous materials. 

LIVE UPDATES: BALTIMORE BRIDGE COLLAPSE 

A National Transportation and Safety Board investigator is seen Wednesday on the cargo vessel Dali, which struck and collapsed the Francis Scott Key Bridge in Baltimore. (Peter Knudson/NTSB/AP)

Some of the hazmat containers were breached, and a sheen was identified in the water that will be dealt with by the authorities. 

NTSB investigators are seen Wednesday looking at the collapsed Francis Scott Key Bridge in Baltimore. (Peter Knudson/NTSB)

Homendy said the investigation would be a "massive undertaking" that is expected to take one to two years. She added that the NTSB will not hesitate to issue urgent safety recommendations during that time frame. A preliminary report is expected in only two to four weeks. 

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NTSB investigators on the bridge of the cargo vessel Dali on Wednesday. (Peter Knudson/NTSB)

Two bodies were removed from the waters of the Patapsco River on Wednesday. 

NTSB investigators have managed to get onboard the Dali, which remains stuck in Baltimore. (Peter Knudson/NTSB)

Four construction workers remain missing and are presumed dead following Tuesday’s collapse. 

NTSB investigators are seen onboard the cargo ship Dali, which struck the Francis Scott Key Bridge in Baltimore on Tuesday, causing it to collapse. (Peter Knudson/NTSB)

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"Based upon the conditions, we're now moving from a recovery mode to a salvage operation because of the superstructure surrounding what we believe are the vehicles and the amount of concrete and debris; divers are no longer able to safely navigate or operate around that in the areas around this wreckage," Maryland State Police Superintendent Col. Roland Butler said Wednesday. 

Fox News’ Chris Pandolfo and Bradford Betz contributed to this report.