Timelapse video shows exact moment ship lost control and crashed into Baltimore bridge

A timelapse has revealed the moments leading up to the collapse of a bridge in Baltimore which has become a 'mass casualty' event.

The Francis Scott Key Bridge (which is often shortened to Key Bridge) opened in 1977 and spans 1.6 miles across the Patapsco River.

The four-lane wide overpass was reportedly used by as many as 31,000 people a day.

However, there's now an empty path where the bridge used to stand after a huge cargo ship plowed into the structure in the early hours of this morning (March 26).

The ship hit one of the bridge's main pillars and the overpass, which is said to have cost $110 million to build, crumbled in the water below in a matter of seconds.

The vessel was travelling eight knots at the time.

The incident has since been declared as a 'mass casualty event' as it's believed at least seven people and several vehicles may have fallen into the river when the bridge collapsed.

At the time of writing, six workers are said to remain unaccounted for.

CCTV footage showed plumes of smoke coming out of the ship as the freighter lost power - something which is also seen in a timelapse video of the incident shared on social media.

Kevin Dietsch/Getty Images

The video begins around 1.23am, when the cargo ship blacks out a minute later.

There's some element of recovery shortly after with a handful of the ship's lights turning back on, but thick smoke quickly followed.

Around 1.26am, the video shows the ship losing power for a second time and, just as its lights came back on it mowed into the bridge - bringing the structure crumbling down.

It's since been confirmed that those on the ship issued a mayday call that potentially saved dozens of lives.

Maryland Gov. Wes Moore said that when the freighter lost power they issued the call shortly before the crash.

While it all happened extremely quickly, the call allowed police to halt vehicle traffic headed over the bridge, Washington Post reports.

Mark Wilson/Getty Images

"By being able to stop cars from coming over the bridge, these people are heroes. They saved lives," Moore said during a press conference.

Elsewhere, Moore spoke of how the incident has shaken the whole community.

"The words that the Key bridge are gone - it still shakes us because for 47 years, [the bridge] is all we've known," he said.

"This is not just unprecedented for what we're seeing and what we're looking at today, it's heartbreaking."

A National Transportation Safety Board team is expected to soon launch an investigation into the matter.