The Argentine news agency Telam reported that Duran's injuries include a collapsed lung and several broken ribs. He was in stable condition after undergoing surgery on Thursday.
The 50-year-old Panamanian boxer was riding with his son, Roberto, and two reporters when the car crashed into another before both vehicles hit a retaining wall, according to Telam.
Duran's son suffered minor injuries, but the reporters -- Ruiz Diaz, a journalist working for Telam, and Luis Gimenez -- were more seriously hurt. Diaz was in a coma and Gimenez broke several ribs.
A winner of four world titles, Duran has refused to retire and lost to Hector Camacho in a fight three months ago. Known as "Hands of Stone", Duran has a 104-16 career record, but is probably best known for saying the infamous words "No mas" when he quit during the eighth round of his rematch fight against Sugar Ray Leonard in 1980.
Duran won his first title in 1972 at the age of 21, taking Ken Buchanan's WBA lightweight crown. His most famous victory came over Leonard for the WBC welterwight title in 1980 before the embarrassing rematch later that year.
Duran also held the junior welterweight and the WBA middleweight titles.