Construction crews were performing 'routine' concrete repairs on 47-year-old Baltimore bridge when ship Dali slammed into concrete pillar causing it to crumble in SECONDS - sending eight workers into river with six still missing

Construction crews had been performing concrete repairs on the Francis Scott Key Bridge when it collapsed on Tuesday morning, officials said. 

Maryland Department of Transportation Secretary Paul Wiedefeld said that eight workers had been repairing potholes when the bridge was hit by a cargo ship. 

Six of them remain unaccounted for following the collapse, which was caught in dramatic video as it collapsed into the Patapsco River.

Wiedefeld said: 'We know there were individuals on the bridge at the time of the collapse, working on the bridge, contractors for us.

He said the workers were 'basically doing some concrete deck repair', but said they did not know how many vehicles were involved.

Maryland Department of Transportation Secretary Paul Wiedefeld, seen here, said that six workers had been repairing concrete ducts when the bridge was hit

The six individuals remain unaccounted for following the collapse, which was caught in dramatic video which showed the 1.6 mile bridge collapse

A representative from Brawner Builders told NBC News that the company had a crew on the bridge when it collapsed.  

Wiedefeld added that the transport authority has set up a facility for family members of those who were believed to be on the bridge at the time of its collapse.

On Tuesday, Maryland Governor Wes Moore also said that a preliminary investigation into the collapsed pointed to it being an accident. 

He said: 'The preliminary investigation points to an accident. We haven't seen any credible evidence of a terrorist attack.'

Moore said the cargo ship reported losing power just before it crashed into the bridge.

He said that a mayday call from the ship allowed officials to limit traffic on the bridge before the crash.

Governor Moore also said that the bridge, which was opened in 1977, was 'fully up to code' and had no structural issues. 

Rescue teams are now racing to save up to 20 people who were plunged into the water following the collision. 

The ship - the Singaporean-flagged Dali - was 20 minutes into its journey when it slammed into a support column on the bridge. 

Maryland Gov. Wes Moore, left, speaks during a news conference as Sen. Chris Van Hollen ( looks on near the scene 

Maryland Governor Wes Moore also said that a preliminary investigation into the collapsed pointed to it being an accident

The ship - the Singaporean-flagged Dali - was 20 minutes into its journey when it slammed into a support column on the bridge

It remains unclear what led to the crash. Video shows the ship going dark seconds before the collision, suggesting a power failure on board. 

In the meantime, Maryland authorities are using sonar detection devices to search for the vehicles that plunged into the 47F water.

Baltimore Fire Chief James Wallace could only confirm that two people were pulled from the water, both are now believed to have been workers.

One was unhurt, the other had to be rushed to a local hospital with 'serious injuries', he said.

It remains unclear  what caused the ship to crash into the bridge in what one official called a 'developing mass casualty event'.

The ship was not being piloted by its own crew but by local pilots who are used to specifically avoid accidents. 

The ship crashed into one of the bridge's supports, causing the structure to snap and buckle at several points

Rescue personnel gather on the shore of the Patapsco River

'Never would you think that you would see, physically see, the Key Bridge tumble down like that. It looked like something out of an action movie,' said Baltimore Mayor Brandon Scott, calling it 'an unthinkable tragedy.'

The ship left Baltimore's Seagirt Marine Terminal at 12:24am, at 1:25am, it began to slow and diverted off of its course. 

The Dali ship was bound for Colombo, Sri Lanka. It's unclear what cargo it was holding. The vessel was due to land in Asia on April 27. 

According to the ship's owners, all crew members were accounted for with no injuries reported. 

Around 30,000 vehicles use the bridge, which is named for the writer of the Star Spangled Banner, every day. It opened in 1977.