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A bicyclist who claims he was hurt in last week's deadly bridge collapse in Miami filed the first civil lawsuit Monday in the case, accusing builders of reckless negligence.

Marquise Hepburn, 24, is suing various design and engineering companies involved, including Munilla Construction Management and partner Figg Bridge Engineers.

Hepburn was biking to work Thursday afternoon just as the 950-ton span buckled onto busy Southwest Eighth Street, his attorney, Matt Morgan, said at a news conference. A car veered into Hepburn's path to avoid being entrapped, he added, knocking him off of his bicycle and leaving him caught amid the rubble.

Morgan did not detail Hepburn's injuries, but said he was hospitalized and is now on a variety of medication.

"He remains in a bad way and he's recovering," Morgan said.

Hepburn is seeking damages in excess of $15,000, although Morgan estimated lawsuits could top $1 billion in claims.

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This initial suit in Miami-Dade Circuit Court comes as investigators work to unravel what caused the tragedy — and follows the revelation that a Figg engineer working on the bridge warned state officials two days earlier that he had seen cracks in the concrete structure.

The warning was left in a voicemail that was only heard Friday because the recipient of the call had been out of the office on assignment, the Florida Department of Transportation said.

Related: Police believe all victims found in Florida bridge collapse

MCM and Figg did not immediately respond to a request for comment about the lawsuit, but have previously said they are working with investigators.

Six people died and eight people were injured in the collapse, according to officials.

Morgan said his client's case hinges on what officials knew about the span's integrity and "why were vehicles allowed to travel underneath that bridge if the bridge might have been in a vulnerable state?"

The section of walkway was dropped into place March 10, but wasn't scheduled to open until 2019, when it would have connected Florida International University with the city of Sweetwater.

The university did not design or build the bridge, but awarded the contract as part of a federal transportation grant.

Recovery operations continue Saturday morning, March 17, 2018, at the site of the Florida International University-Sweetwater University bridge in the Miami area that collapsed during construction earlier in the week. Pedro Portal / Miami Herald via AP

The 174-foot-long section was part of a larger bridge being built that was designed to withstand hurricane-force winds. The method of "accelerated bridge construction" that was being used is considered innovative because it allows a bridge to be assembled on site in a short amount of time with minimal traffic disruption.

Sen. Marco Rubio, R-Fla., told "Meet the Press" on Sunday that the National Transportation Safety Board is testing the salvaged concrete as part of its investigation. He said he couldn't confirm earlier reports that workers were specifically "stress testing" the span at the time of the collapse.

"What we do know is that there was work ongoing. There are these rods that go inside [the bridge], they're like cables, and they were being tightened," Rubio said.

"Whether the work was the cause of it or not remains to be seen," he added.

Students from FIU held a moment of silence Monday afternoon for the six victims. Among those killed was 18-year-old FIU student Alexa Duran, whose uncle has demanded accountability.

"I want people to step up and say, 'Hey, I was the one responsible,'" said Joe Smitha, according to NBC Miami. "Come out of the shadows. Where are you people? This was a colossal failure of the system and this was complete incompetence from the top down."