Federal regulators proposed an $11,200 fine Tuesday against Chicago Bridge & Iron Co. because its workers in southwest Louisiana dropped a prefabricated section for a new nuclear power plant in South Carolina and then tried to cover it up, officials said.

The accident happened March 1, 2013, at the CB&I manufacturing plant in Lake Charles, which became part of CB&I after the company acquired The Shaw Group Inc. in Baton Rouge in February 2013.

The facility makes prefabricated parts for two nuclear power plants under construction in Georgia and South Carolina.

While moving a large component, the load swung violently, dropped several feet and hit the floor because it was improperly secured, according to an NRC summary published in December. NRC investigators said a rigging manager and a safety representative told CB&I workers who witnessed the accident to omit in their reports that the large submodule had struck the floor.

About a week later, one of the crew members reported the accident, prompting the company to start an internal investigation. However, the same rigging manager involved was assigned to the subsequent investigation and falsely claimed there was no evidence of a fall, authorities said.

An NRC official responsible for construction oversight, Michael Cheok, said the employees engaged in deliberate misconduct. He accused the firm’s managers and workers in a Dec. 14 letter of “placing production and schedule concerns ahead of safety and quality.”

CB&I spokeswoman Gentry Brann did not immediately return messages seeking comment. NRC officials said more recent inspections show the plant’s performance has improved.

The part was scheduled to be installed at the V.C. Summer nuclear plant near Columbia, South Carolina. CB&I and utility officials inspected the dropped component after the accident and determined it was safe.

“SCE&G is confident in the quality of the modules we have received from the CB&I facility in Lake Charles,” said Rhonda O’Bannion, a spokeswoman for plant co-owner SCE&G.

CB&I’s plant in Lake Charles has struggled to meet the nuclear industry’s strict quality rules and the production deadlines for the two nuclear plants under construction. The utility companies who own those nuclear plants have all announced significant delays and cost overruns.

Some of the prefabricated parts that CB&I was supposed to make for the new plants were contracted to other firms.

CB&I stock fell 7 cents Tuesday, closing at $51.24.