The sheriff's office said Mars was driving a 2004 Porsche SUV near Aldie Friday that "for unknown reasons" crossed the center line and struck an oncoming minivan, The Washington Post reported Tuesday.
A passenger in the minivan, Irene C. Ellisor, 86, of Huntsville, Texas, who wasn't wearing a seat belt, died at the scene. Others in the minivan were injured.
They were in Virginia for a family wedding.
Mars, with a net worth estimated in the billions, is an owner of Mars Inc., the McLean, Va.-based candy, food and beverage firm with annual sales of more than $30 billion. She will be 74 this week.
The sheriff's office said the matter was "pending review by the Office of Commonwealth's Attorney."
Mars' involvement was first reported by Leesburg Today and was confirmed Tuesday by the sheriff's office, the Post said.
A Mars spokesman said in a statement Tuesday she was "involved in a two-vehicle accident" in Loudoun and recuperating at home after being hospitalized for her injuries.
"This tragedy has left Jacquie filled with sorrow for the loss of life and those who were injured," spokesman Kent Jarrell said in the statement. "She would like to express her deepest condolences to the families involved."
He said the crash was "a private family matter, not a company matter."