How could the FIU pedestrian bridge collapse have happened?

SANTA CLARA, Calif. (KGO) -- The speed in which the FIU pedestrian bridge was built was not likely the problem.

That's what Professor Reynaud Serrette, Ph.D. told ABC7 News.

"Fast-tracking is not a big deal. I think Arnold Schwarzenegger did it when he was governor. He said I will give you money for each day you save in construction and people got it done and we had no failures," said Serrette who is the chair of the Civil Engineering Department at Santa Clara University.

RELATED: At least four dead after bridge collapses onto busy Florida highway

He said it's too soon to know exactly what went wrong... that there could have been a problem with the design, materials, construction or placement.

Serrette wonders if there's a video of the collapse. He said that would help investigators determine what happened.

The bridge is known as an "ABC" bridge-that stands for accelerated bridge construction.

Some dub it an instant bridge. The span was built on the side of the road and then moved into place in a matter of hours over the weekend-- with little disruption of traffic.

"It usually is safer because they're doing all the construction away from the traveling public," said Andy Herrmann, past president of the American Society of Civil Engineers.

800 bridges have been built this way or with pre-built elements since 2010.

The Federal Transportation Department lauds this type of construction and paid most of the $14 million for the bridge-- it was supposed to withstand a Category 5 hurricane and last 100 years.

RELATED: Collapsed FIU bridge was installed recently

Just days before the bridge collapsed, Jorge Munilla the president of MCM (the contractor that built and installed the bridge) said, "I'm exhaling now because it has been set. The challenge is, we have mitigated the challenges by doing exhaustive studies and work plans with all the different members that formed the team that are delivering the project today."

The Florida Department of Transportation has released a preliminary fact sheet on the collapse.

Professor Serrette said the following item from the FDOT is noteworthy: "Under the terms of the procurement issued by FIU and due to the unique characteristics of the design of the bridge, an independent, secondary design check was required. Under this project, it is the responsibility of FIU's design build team to select the firm used to conduct the independent, secondary review. The firm selected, Louis Berger, was not FDOT pre-qualified for this service, which is required under FIU's agreement with the state. FIU's design build team is responsible for selecting a pre-qualified firm and ensuring this process is followed."