A video taken on the dashcam of a car as it approached Miami's FIU bridge seconds before it collapsed last week has captured the moment it fell down on traffic, revealing that there was a worker on top of it at the time, wrote dailymail.co.uk.

The footage shows the man working on the top left corner of the bridge as cars passed beneath it. 

When it suddenly collapsed, the man was thrown into the air then fell among the rubble.

It is not clear if the man is Navarro Brown, a 37-year-old employee of Structural Technologies VSL, who was working at the site and was among the six killed, or if others were there and walked away injured.

The footage also reveals how stunned motorists and passengers in vehicles which hadn't yet reached the structure rushed to help after the accident.  

The bridge was behind schedule and over budget at the time. 

An official cause for the collapse is yet to be given but engineers were examining a crack in one side of it at the time.  

On Wednesday, it was revealed that the crash happened after changes to the bridge's design were made. 

When the bridge collapsed last Thursday, a stress test was being performed to assess its strength. 

US Senator Marco Rubio suggested on Twitter last week that officials were tightening cables which supported the structure when it collapsed but he gave no additional information. 

Experts have been hesitant to blame the failure on one thing alone and have suggested instead that there were many reasons for the failure. 

Among them could be the redesign which involved the shifting of a tower. 

Henry Petroski, a Duke University civil engineering professor, said even seemingly minor changes in a bridge's design can lead to failures.

'Once a design is completed, subsequent modifications tend to be suggested and approved without the full care that went into the original design.

'This has happened time and again in bridges and other engineering structures,' he said.  

More than 700 people gathered to honor the six victims in the horrific accident. 

A student-led vigil was held at the university on Wednesday and featured a number of touching tributes to Duran, the youngest victim. 

Michaela Reyes and Sofia Rincon, two of Duran's closest friends from high school, performed the Rihanna song Stay as tribute to the teen during the vigil.

'No one will be able to understand how I feel. Alexa was my world and my life,' her mother, Gina Duran, told The Associated Press. 'Nothing will ever be the same.'

FIU president Mark Rosenberg presented flowers to the family before they prayed at the site of a memorial for Duran and the five other victims. 

Rosenberg encouraged mourners to 'grieve together, to heal together' as he spoke at the vigil. 

'This is a strong community, a caring community, a community that will comfort one another through this, this is a community that rises time and again,' he said.  

'We are going to the carry the memory of the victims, we'll carry that memory forever. Now is the time to grieve together, to heal together.' 

'So let our sadness galvanize us to stay the course of goodness and on promoting the hope and opportunity that will enable our community to rise stronger, to rise wiser, and to rise better as a consequence of this terrible loss.'