New videos show construction workers laboring on a pedestrian bridge in Florida shortly before it collapses, killing six people.

The time-lapse video released Wednesday by Florida International University shows the four construction workers using a crane hoist to perform work on the bridge.

A preliminary report from the National Transportation Safety Board suggests investigators are focused on cracks in the south and north ends of the bridge near a Miami-area university campus.

The cracks were discovered in the days before the March 15 collapse, which killed a bridge worker and five people in vehicles crushed by the falling structure.

The bridge was to have spanned a busy highway and canal and connected Florida International University’s campus to the neighboring community of Sweetwater.

(AP)