Miami • As Florida authorities work to identify the people who died in Thursday’s catastrophic bridge collapse, state and federal investigators will begin the task of figuring out how and why the 5-day-old span failed.

Miami-Dade County Fire Chief Dave Downey said Thursday night that his crew is using high-tech listening devices, trained sniffing dogs and search cameras in a race to find anyone still alive in the rubble. The $14.2 million pedestrian bridge was supposed to open in 2019 as a safe way for students to cross the busy road. It linked the community of Sweetwater with the campus of Florida International University.

“We have to remove some of this piece by piece. It’s very unstable.” Aerial footage at the site showed a trained dog running atop fallen concrete and sniffing in the crevices for any victims,” he said.

But Miami-Dade Police Director Juan Perez acknowledged the likelihood of finding more victims under the rubble is slim.

“We know that there’s going to be a negative outcome at the end of the day,” Perez said.

Four people were found dead and at least nine others were injured and taken to local hospitals; officials at one point said 10 were injured.

Florida Gov. Rick Scott and U.S. Sen. Marco Rubio attended the evening briefing.

Rubio said the public and the families of the dead and injured deserve to know “what went wrong.”

Scott added that an investigation will get to the bottom of “why this happened and what happened.” He said that if anyone did anything wrong, “we will hold them accountable.”

National Transportation Safety Board chairman Robert Sumwalt III said a team of specialists was heading to Miami on Thursday night with plans to begin its investigation Friday morning.

Rubio, who is an adjunct professor at the school, noted the pedestrian bridge was intended to be an innovative and “one-of-a-kind engineering design.”

An accelerated construction method was supposed to reduce risks to workers and pedestrians and minimize traffic disruption, the university said. The school has long been interested in this kind of bridge design; in 2010, it opened “The ABC (accelerated bridge construction) Center,” to help bridge professionals. Other universities around the country partnered with FIU to “provide the transportation industry with the tools needed to effectively and economically utilize the principles of ABC to enhance mobility and safety, and produce safe, environmentally friendly, long-lasting bridges.”

Renderings showed a tall, off-center tower with cables attached to the walkway to support it. When the bridge collapsed, the main tower had not yet been installed, and it was unclear what the builders were using as temporary supports.

The project was a collaboration between MCM Construction, a Miami-based contractor, and Figg Bridge Design, based in Tallahassee. Figg is responsible for the iconic Sunshine Skyway Bridge across Tampa Bay.

Figg issued a statement Thursday saying the company was “stunned” by the collapse and promising to cooperate with investigations.

“In our 40-year history, nothing like this has ever happened before,” the company’s statement said. “Our entire team mourns the loss of life and injuries associated with this devastating tragedy, and our prayers go out to all involved.”

MCM Construction Management, which is building the bridge, posted a message to the company’s Facebook page promising “a full investigation to determine exactly what went wrong.”

Robert Bea, a professor of engineering and construction management at the University of California, Berkeley, said it was too early to know exactly what happened, but the decision to use what the bridge builders called an “innovative installation” was risky, especially because the bridge spanned a heavily traveled thoroughfare.

“Innovations take a design firm into an area where they don’t have applicable experience, and then we have another unexpected failure on our hands,” Bea said after reviewing the bridge’s design and photos of the collapse.

The FIU community, along with Sweetwater and county officials, held a “bridge watch party” March 10. That’s when the span was lifted from its temporary supports, rotated 90 degrees across an eight-lane thoroughfare and lowered into its permanent position over the busy road.

FIU President Mark Rosenberg said during a news conference that tests were being done on Thursday. Authorities said two construction workers were on the bridge when it collapsed; it’s unclear what the tests were or if they contributed to the failure.

“This bridge was about goodness, not sadness,” Rosenberg said. “Now we’re feeling immense sadness, uncontrollable sadness. And our hearts go out to all those affected, their friends and their families. We’re committed to assist in all efforts necessary, and our hope is that this sadness can galvanize the entire community to stay the course, a course of goodness, of hope, of opportunity.”

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