A beautiful autumn day was marred by tragedy Thursday when a construction accident at the site of the new Interstate 10 Twin Span bridge sent 10 workers plunging into Lake Pontchartrain.

It happened just after noon when a steel girder snapped, flinging men, concrete and equipment into the water 35 feet below. The Special Operations division of the St. Tammany Sheriff’s Office responded immediately, and nine of the men were quickly rescued with nothing more than broken limbs, although one was airlifted to Lakeview Regional Medical Center and another was transported to Slidell Memorial Hospital.

Personnel from Louisiana Wildlife & Fisheries and the U.S. Coast Guard assisted in the search for the 10th man. With the help of rescue divers, officials are believed to have located him by about 2 p.m., trapped beneath a large amount of debris and presumed dead. “We have to try and remove the debris before we can take him out,” said Sheriff Jack Strain, whose team was waiting on a large crane to be brought in to remove several large pieces of concrete at presstime Thursday. “The position it’s in can make it much more dangerous, and that will determine how we raise it.”

Calling the accident a “horrible tragedy,” Strain praised the actions of all personnel, including Fire District 1, which assisted with first aid and triage. He said the workers told him they had never seen an accident like it.

All of the workers involved are believed to be employees of Boh Brothers, the construction company that is the main contractor on the project. Strain said it was unclear if the men were tethered to the platform before it snapped, but the company’s safety policy usually requires them to do so.

“From what I understand, what they were doing is normally the safest phase of this type of construction,” he said. “It will take some time to determine exactly what caused this.”

Representatives from OSHA, state safety officials and Boh Brothers engineers will all be involved in the investigation.