Three construction workers were presumed dead when they fell Wednesday from the Interstate 430 bridge into the Arkansas River, a rescue official said.

Workers for a contractor hired by the Central Arkansas Water utility fell 100 feet to the river shortly before 11 a.m. More than an hour later, a fire department official said the men were presumed dead and the rescue operation had turned into a recovery effort.

Little Rock Fire Department Capt. Jason Weaver said the men were not spotted by 12:15 p.m., about 1 1/4 hours after their fall.

Recovery crews had hooked what appeared to be the scaffolding, and the original plan was to bring a barge in to raise the structure. But the scaffolding, laden with equipment, weighs as much as 10,000 pounds. So officials opted to close northbound traffic lanes on Interstate 430 at 6 p.m. and use a crane to raise the platform.

The platform was big enough to hold the men, two generators and a welding machine, Weaver said. "A lot of metal, a lot of weight," he said.

The river, swollen from recent rains, was moving too swiftly for divers to search the waters.

Four men were on the platform and one was able to hold on and call for emergency help before he was rescued, said Pulaski County Sheriff's Office spokesman John Rehrauer.

Charles Jackson, a worker on the project, said he'd been on the platform earlier in the day and noticed no safety problems. He said he knew the three missing men well.

Jackson said that if the men were tethered to the platform, for safety reasons, they would be able to get unhooked.

Marie Crawford, a spokeswoman for Central Arkansas Water, said the men were employed by Oscar Renda Contracting Inc. of Roanoke, Texas. She said the utility contracted the Texas company in April 2006 to install two sections of 30-inch-diameter waterlines under and across the bridge.

The installations are part of a $43 million project to increase the utility's capacity to deliver water to water systems in the area.

Corey Wells, treasurer and controller for Renda Contracting, said the company was aware of the accident and was contacting family members of the missing workers.