Three construction workers died trying to save a fourth man who fell into a collapsing trench, according to officials in northeast Nebraska.

The Knox County Sheriff's office said the four men were working on the drainage trench Friday morning when a part of it collapsed.

Officials said 24-year-old Travis Lunn of O'Neill fell into the collapsing trench. The three others tried to rescue him and also became trapped in the dirt, officials said.

Killed were Lunn, David Peterson, 35, of O'Neill, Gary Forsch, 61, of Spencer and Brad Kelly, 43, of Lynch.

The collapse was reported around 9:15 a.m. Friday along state Highway 12 near Verdel.

Verdel is a town of about 60 people less than 10 miles from the South Dakota border.

Officials have ordered autopsies, and an investigator with the Occupational Safety and Health Administration was headed to the scene.

The men were working for Prouty Construction in O'Neill.

The company referred questions to attorney Jack Wolfe of Lincoln. He didn't immediately return a phone call Friday afternoon.

No telephone listings were found for Kelly, Lunn or Peterson. Calls on Friday afternoon to a listing for Gary Forsch in Spencer went unanswered.

The six-mile, $2.26 million project was scheduled to be completed in October, according to the Nebraska Department of Roads Web site.

The roadway has been damaged by flooding because of high Missouri River water levels. Flooding had saturated the roadway embankment, creating potential for erosion, according to the U.S. Army Corps of Engineers in Omaha.

It hadn't rained in a few days in the area, but sheriff's officials said water appeared to be seeping into the trench at the site of the collapse.