PROVIDENCE, R.I. — A group that owns several well-known Gilded Age Newport mansions was cited by federal workplace safety inspectors for allegedly exposing workers to lead-based paint and potentially fatal falls, the U.S. Department of Labor’s Occupational Safety and Health Administration said Thursday.

The Preservation Society of Newport County was cited for 10 serious violations, which means there is substantial probability for death or serious physical harm, OSHA said. The agency proposed $51,840 in fines.

The society’s mansions include The Breakers, The Elms and Marble House, and are among the most visited tourist sites in New England.

Inspectors opened an investigation on May 8, when two OSHA inspectors happened to be driving past Chateau-sur-Mer on Bellevue Avenue and noticed employees working on a ladder at an outbuilding that was not properly placed, spokesman Ted Fitzgerald said.

“Falls are a particular concern for OSHA because they are the No. 1 killer in construction work,” he said.

The subsequent investigation found that workers were not taking proper precautions when working with lead-based paint, Fitzgerald said.

“The society’s care and maintenance of historic structures should not come at a cost to the health and well-being of its workers,” said Patrick Griffin, OSHA’s area director for Rhode Island.

Preservation society spokeswoman Andrea Carniero said in a written statement that it has an outstanding safety record and has never before been cited by OSHA. She said its relevant employees all receive training on how to deal with lead paint and that the society is working with OSHA on the problems.