Key Bridge collapse: A timeline of the tragedy in Baltimore

Early Tuesday morning, a large container ship left port in the Baltimore Harbor, bound for Colombo, Sri Lanka. But the vessel never made it out of the harbor and disaster struck minutes after it set sail. 

Just before 1:30 a.m., the ship lost power and could no longer steer. Going at about 8 knots — roughly 9 mph — the ship ran into a pillar on the Francis Scott Key Bridge. Within seconds, the structure broke down, sending construction workers and several vehicles plunging into the frigid water below. The vessel then caught fire, sending black smoke billowing into the air.

Now, authorities and first responders are hours into the search for at least six people known to have fallen into the Patapsco River following the shocking collapse. The missing individuals were part of an eight-person construction crew working to fill potholes on the bridge. 

READ MORE: 6 presumed dead in Baltimore bridge collapse, says employer

First responders were able to pull two people from the river almost immediately. One of those rescued was taken to Baltimore's Shock Trauma Center. The second person declined treatment. 

It's not yet clear if other individuals may have fallen into the river at the time of the collapse but officials said early on in the investigation that sonar had detected the presence of several cars in the water. 

As the search and investigations continue, here's what we know about the moments leading up to the disaster: 

The National Transportation Safety Board, which is leading the investigation into the collapse, says it arrived on scene around 6 a.m. 

In an afternoon press conference, National Transportation Safety Board Chair Jennifer Homendy remained tight-lipped about the search and rescue efforts, only saying that they are ongoing. 

The FBI, Coast Guard and several Maryland agencies are assisting in the search with multiple dive teams reportedly working the scene.