An ironworker fell to his death yesterday when one of nine 150-foot light towers at Atlanta's unfinished Olympic Stadium buckled, unleashing two banks of lights onto workers below. Two other workers were injured, one seriously, when lights fell from the weakened structure and crashed to the 85,000-seat stadium's concrete bleachers.

The cause remained unclear, according to Chuck Winstead, project director for Atlanta Stadium Constructors, the general contractor. Construction was halted as an investigation began, but officials said work could resume today.

As constructed, the tower resembled an inverted L with two light banks attached to the ends of its horizontal beams. The worker who died was hanging from the top section on a safety harness when it folded in.

Officials identified the dead man as Jack L. Falls of McDonough, Ga.

Witnesses said the dead man landed a few feet below one of the light banks, which fell away from the tower as it collapsed. The second worker, David Oakes of Franklin, Ga., who was hospitalized in satisfactory condition, suffered hip and head injuries when a light bank fell on him, authorities said. One other worker was treated at an occupational clinic and released.

The $207 million stadium will be the site of the 1996 Summer Games' opening and closing ceremonies, as well as track and field events. It is scheduled for completion by January.