
Timelapse videos of the construction and installation of the new pedestrian bridge which collapsed at Florida International University on Thursday reveals its quick - and now controversial - construction method.

The bridge was installed less than a week ago after months of construction - using a method called Accelerated Bridge Construction, or instant bridge, according to a press release sent out by the University.

Instant bridge is a method meant to reduce risk to construction workers and pedestrians and to prevent traffic buildup - but is now being called into question after Thursdays incident, which killed six people.

Senator Marco Rubio tweeted that the bridge came down as steel suspension cables were being tightened in a process known as stress testing.

Experts told the Miami Herald that the process has been responsible for the collapse of at least one bridge in the past, which happened in Australia in the 1970s.

The bridge that collapsed at Florida International University was installed less than a week ago after months of construction - using a method called Accelerated Bridge Construction, or instant bridge, according to a press release sent out by the University. Pictured is the bridge being built in its final stages of construction, which was a many-months-long process

The 174-foot long, 950-ton bridge was built over the course of several months on the side of the busy seven-lane 8th Street highway - which runs from downtown Miami all the way to the Everglades - where it would eventually be placed over. The bridge is pictured as it is starting to be driven across the road and to its final resting place

At a point in the construction period it was picked up and put onto its position over the roadway. That part of the construction process took a mere six hours to complete. It was up and ready to be used by the public on Saturday. Pictured left is the bridge being rolled into place over the highway, and left is the finished product

The first timelapse shoes the final stages of the construction process into its instillation. It begins showing the bridge being built as it will stand but on the side of the highway. It is then rolled onto the highway and installed into the ground.

The second video specifically shows the six-hour installation process, which started before dawn and saw the bridge, which was on rolling platforms, being wheeled into place.

The video shows construction workers toiling before the sun has risen as they move the building across the busy seven-lane 8th Street Highway - which runs from downtown Miami all the way to the Everglades - and into its place before securing it where it was expected to stand for the next century.

Accelerated Bridge Construction involves prefabricated elements meant to cut installation time, cost and environmental impact. It has also been hailed as 'a paradigm shift in the project planning and procurement approach' by the Department of Transportation's Federal Highway Administration.

The 174-foot long, 950-ton bridge was built over the course of several months on the side of the busy seven-lane 8th Street highway - which runs from downtown Miami all the way to the Everglades - where it would eventually be placed over.

At a point in the construction period it was picked up and put onto its position over the roadway. That part of the construction process took a mere six hours to complete. It was up and ready to be used by the public on Saturday.

Instant Bridge has been hailed as a feat of engineering safety and is said to reduce risk to workers, pedestrians and drivers and have minimal to no impact on traffic flow.

That construction was completed Saturday - and was installed as part of a pedestrian safety initiative aimed at reducing foot traffic along the Highway.

The second video specifically shows the six-hour installation process, which started before dawn and saw the bridge, which was on rolling platforms, being wheeled into place

The video shows construction workers toiling before the sun has risen as they move the building across the busy seven-lane 8th Street Highway

Pictured are workers moving the bridge across the highway as well as into a straight line, all the while making adjustments to its structure

The crew worked in the early hours of the morning before traffic became busy on the highway to install the bridge

The bridge was eventually taken off of its rolling platforms as it was settled into the spot it was expected to stand for up to 100 years

Finally the construction workers get it to a point where it is straight and set across and it can be sunk into the ground using cement beams

MCM Construction and FIGG Bridge Design teamed up on the bridge - which cost a whopping $14.2million, paid for by a nearly $20million grant from the US Department of Transportation.

It was designed to withstand a Category 5 hurricane and to last 100 years, the University said.

The bridge was one part of a larger infrastructural plan at the university in Miami that was set to be completed in 2019.

The plan was going to include a plaza equipped with free wireless internet.

Several bridges in the United States have been built using the instant bridge method - including the Nevada I-15 Bridge, the revamed Massachusetts Cedar Street Bridge and the reconstructed Eastern Avenue Bridge in Washington, DC, among others.

The exact cause of the bridge collapse remains unclear.

'It could be materials, it could be construction technique, it could be the engineering design itself,' Andy Hermann, a former president of the American Society of Civil Engineers told ABC News.

It crumbled onto waiting traffic on the busy highway at about 1.45pm as cars were waiting for lights to change.

US Senator Bill Nelson of Florida told local TV station CBS Miami that between six and 10 people died. Another 10 have been rushed to Kendall Regional Medical Center, at least two in 'extremely critical' condition.

One of those who arrived in critical condition was suffering a cardiac arrest, but was revived by doctors, while the other has a serious brain injury.

The remaining eight were stable, with injuries such as 'bruises and abrasions to broken bones.'

Rescue teams are still working to free eight vehicles trapped in the bridge wreckage, Miami-Dade County Mayor Carlos Giminez said in an interview with CBS Miami.

The brand new pedestrian bridge collapsed without warning on Thursday afternoon, crushing the cars below it

Miami-Dade Fire Rescue Department personnel and other rescue units work at the scene where a pedestrian bridge collapsed. One driver may have had a lucky escape after the front of his car escaped relatively unscathed while the back was crushed