Four thoroughbred racehorses were euthanized after competing at the New Orleans Fair Grounds Race Course in a 10 -day span, prompting criticism from an animal advocacy group.

Washington D.C. based Animal Wellness Action said the deaths started on Jan. 9 with “J Rob”, a 3-year-old colt that had just won a $15,000 maiden claiming race. Two days later “Big Shanty” was killed after pulling up lame. “Jim’s Silverbullet” was killed on the Jan. 16 and “Take Charge Cece” a day later.

Track officials did not specify the circumstances surrounding the deaths said the tracks equine medical director was investigating.

Animal Wellness Action is backing a bill now before Congress that would set national standards for drugging racehorses and place oversight with an independent body under the U.S. Anti-Doping Agency. The bill has found momentum in Congress after race horse deaths spiked last year at Santa Anita Park in California.

“American horseracing is addicted to drugs, and it’s time for an intervention,” Wellness Action executive director Marty Irby said in a statement. “Our modern-day society will no longer tolerate the deaths of these iconic American equines for entertainment — this isn’t ancient Rome, it’s 2020.”

The thoroughbred racing season at Fair Grounds runs through March 29, with the Louisiana Derby on March 21.