Baltimore Key Bridge Collapses, Six People Now Presumed Dead

5:55 PM PT -- The 6 remaining people officials were searching for in Baltimore are now officially presumed dead. A Coast Guard spokesperson said they're suspending their rescue operation. Divers are heading back out again Wednesday to try and recover the bodies.

7:32 AM PT -- Maryland Gov. Wes Moore says crew on the cargo ship were able to issue a "mayday" call before the collision, which enabled authorities to limit traffic on the bridge.

7:18 AM PT -- Officials say 8 people were on the bridge at the time of the collapse, and that thus far -- two of them have been accounted for ... with one in the hospital, and the other being stable. The search for the other six continues.

Maryland's governor also says the crew onboard the ship notified authorities that they'd lost power -- which at this point is leading investigators to believe this was an accident. Video of the vessel losing power at least two different times before it made contact with the bridge has been circulating ... and seems to back this description.

6:18 AM PT -- Dive operations have begun in Baltimore as rescue crews start to search for anybody still in the water. First responders have congregated near a river bank as the sun came up.

A lot of moving parts still, obviously ... and now, they'll attempt to find and save anyone they can.

Baltimore's Francis Scott Key Bridge came crashing down Tuesday after it was struck by a large cargo ship, causing a possible mass casualty incident that was all caught on video.

Check out this stunning footage of the vessel plowing into the steel, arch-shaped bridge, which suddenly collapsed into the Patapsco River and broke into pieces right before our shocked eyes.

Baltimore Mayor Brandon Scott called it an "unthinkable tragedy" that looked like something out of an action movie.

Maryland officials just held a press conference, telling the public what they know so far.

Beginning at 1:30 AM ... 911 callers started inundating the Baltimore Fire Department, reporting what officials later described as a "dire emergency."

Several vehicles crossing the bridge at the time plunged into the river below, but it was unclear how many.

The cargo ship went up in flames after it hit the bridge. Officials at the presser seemed to suggest they were in communication with the ship's crew, whose current status was unknown.

Divers and search crews responded, scanning the frigid waters with sonars for upwards of 7 people and possibly more. Two people have been rescued -- one with serious injuries.

The water temperature is 48 degrees, and authorities say it's virtually impossible to survive for more than 3 hours.

Sonar has detected multiple cars underwater, as the search continues.

Officials said federal and local authorities were investigating what caused the disaster. No word yet on how many victims in total were injured or possibly killed.