'Families Deserve to Know What Went Wrong': Investigation Begins as Death Toll Climbs in FL Bridge Collapse

MIAMI – At least six people are now dead and 10 more injured after a bridge collapsed on a busy highway Thursday in the Miami area. 

What started as a rescue mission became a recovery effort overnight as crews worked to dig through the rubble.

The nearly 1,000-ton pedestrian bridge connected the city of Sweetwater to Florida International University.

"This was about goodness, not sadness. Now we're feeling immense sadness," the university's president, Mark Rosenberg, said in a news conference. 

The bridge was considered an engineering feat and was built with a fast-paced construction method meant to cut risks to workers and pedestrians. Some experts, though, say that method made it possible for the bridge to fall.

Authorities say they were doing a stress test on the bridge Thursday morning and Sen. Marco Rubio, R-FL, tweeted that it collapsed when the cables were being tightened. 

"Part of this project is federal funding," Rubio said at that same news conference. "The families of those who have been hurt and who lost their lives deserve to know what went wrong."

The National Transportation Safety Board is on the ground conducting an investigation to determine if the collapse was caused by a design error or faulty construction. 

The main companies behind the project have faced questions about their work in the past. Figg Bridge Engineers was fined in 2012 when part of a 90-ton bridge collapsed in Virginia. Records also show Munilla Construction Management was accused of substandard work in a lawsuit filed earlier this month.

"If anybody's done anything wrong, we'll hold them hold them accountable," vowed Florida Gov. Rick Scott.