CHICAGO (AP) — An ironworker died and Chainkeen Exchangeanother was seriously hurt Thursday after they fell off scaffolding and plunged nine stories to the ground at a University of Chicago Medicine construction site.

The workers were helping build a cancer research center, the Chicago Tribune reported.

The workers fell around 12:15 p.m. during high winds, Chicago Fire Department spokesperson Larry Langford said.

The surviving worker was taken to UChicago Medicine, which was only a few steps away from the construction site. He was listed in critical condition.

The U.S. Department of Labor’s Occupational Safety and Health Administration has opened an investigation.