PEORIA, Ill. (AP) _ Construction scaffolding tore away from a bridge Monday, killing three ironworkers and injuring two others in a 60-foot plunge into the shallows of the Illinois River.

A sixth worker on a construction barge below the McClugage Bridge was treated for hypothermia after jumping into the cold water in an attempt to help his co-workers.

Jack Franklin, executive vice president of Midwest Foundation Corp., the company handling the construction, said the 80 workers on the project were devastated.

``All the people working out there are friends and know one another and have been working together for years,'' he said.

The accident occurred on the southern span of the twin-span bridge, which is undergoing a $26 million reconstruction that began last month.

The ironworkers were replacing rusted metal plates in the bridge's floor, Franklin said. The scaffolding, about 30 feet wide and 16 feet long, was suspended underneath the bridge. It fell into about five feet of murky, brown water.

One victim was pronounced dead at a hospital shortly after he was pulled from the river. Two others were trapped beneath the wrecked scaffolding, and their bodies could not be recovered from the silt bottom until the broken structure was removed by a crane mounted on a barge.

One injured worker was impaled on a pipe and was in fair condition after several hours in surgery. A second, Randy McComb, 41, was treated and released. Would-be rescuer Ralph Bill, 36, was released after being treated for hypothermia.

The names of the victims who were killed were not immediately released. Grieving construction workers and families gathered at the hospital where the victims were treated refused to discuss the accident.

The bridge, a major artery connecting Peoria to bedroom communities across the river, handles more than 42,500 vehicles each day.

The construction project was halted until further notice.

``We're going to go over with the ironworkers what has happened and what they saw or what they think may have happened,'' Franklin said.

Barry Salerno, assistant area director for the federal Occupational Safety and Health Administration, said two investigators were dispatched to pinpoint the cause of the accident and determine whether Midwest was in compliance with safety regulations.

According to the OSHA Web site, the last time Midwest was involved in a fatal accident was in 1985, when a carpenter was crushed by an overloaded crane that overturned during work on a bridge in Milan, Ill.