An "I-4 Ultimate" worker was killed when reinforced steel fell on top of him at a work site off Interstate 4 in downtown Orlando on Thursday morning.

Michael Tolman, 56, an ironworker for SGL subcontractor Shelby Erectors, was struck at about 10 a.m. by rebar forming a "cap cage" near the westbound I-4 on-ramp at South Street, the company and police said.

Tolman was taken to Orlando Regional Medical Center in critical condition, where he died.

Work has been halted along the entire 21 miles of I-4 Ultimate project construction, SGL said.

"We are investigating all of the factors that led to this incident, and all protocols following such an incident are being followed," SGL said in a released statement. "In the meantime, our focus is on the injured person and supporting him."

The cause of the accident has not been determined, and SGL will conduct an investigation along with authorities, the company said.

"We are supporting individuals and families as they deal with this tragic event. We want to thank the police, fire and local EMS for their rapid response," an SGL statement said.

Another construction worker on the I-4 Ultimate project on Feb. 25, 2016 was killed when a dump truck in the work area backed up into Marvin Franklin, 34, of Orlando. Curtis Popkey, a subcontractor working the project on Dec. 20, 2016 was also killed on the job when he was struck by a steel stand. 

"I-4 Ultimate" is a $2.3 billion, years-long construction project along a Central Florida stretch of the interstate that traverses Florida. The project spans from west of Kirkman Road in Orlando to east of State Road 434 in Longwood. Work is expected to last until at least 2021.