Descendants of Triple Crown-winning Thoroughbreds Secretariat and Seattle Slew were among six horses killed when fire swept through their Round Lake, Ill., barn on March 10.

In 1973 Secretariat won the Kentucky Derby, the Preakness Stakes, and the Belmont Stakes–the three races that comprise the Triple Crown. Seattle Slew became the next to last horse to win the series in 1977 (Affirmed won it in 1978).

Round Lake Fire Marshall Doug Ziegler said that around 1:30 p.m. on March 10, firefighters responded to a fire in a barn owned by Urbano Hernandez. A total of nine horses were residing in the barn at the time of the fire, Ziegler said. Of those, six were killed in the blaze including a stallion descendant of Secretariat named Secret Slewrisky, Zeigler said. Another stallion, a descendant of Seattle Slew named A.P. Indy Prince, was also killed in the blaze, Zigler said. Four mares, one of which was pregnant, also died in the fire.

Hernandez was unavailable for comment