In response to four horse deaths following chuckwagon races at the 2015 Calgary Stampede, event administrators have promised a full review of the rodeo’s safety protocols and policies.

The GMC Rangeland Derby chuckwagon race takes place each year at the Calgary Stampede, held annually in Alberta, Canada. The event pits four teams of horse-drawn wagons and outriders against each other in a series of elimination races over several days. In 2015, 36 drivers and 216 horses competed for more than $1 million in prize money, the event’s website said.

In recent years, several horses have died in the chuckwagon races.This year, four horses used in the event were euthanized due to injuries sustained during the races.

In response to the deaths some humane groups, including the Vancouver Humane Society (VHS) have called for the immediate suspension of the chuckwagon races pending an independent review of the event’s safety