The British Horseracing Authority said the fatalities would be “looked at in detail” as part of standard protocol to improve racehorse safety.
James Given, BHA’s director of equine regulation safety and welfare, said: “We are all devastated about the fatal injuries this week and our thoughts are with everyone connected with the horses.”
He said the fatal injury rate of racehorses had been reduced to fewer than five in every 1,000 runners, which was also the rate at Cheltenham over the last five years.
He added: “Risk can never be entirely eliminated.”
Given told Racing TV Envoi Allen had “almost certainly” had a “very acute cardiovascular collapse”.
“It happened very quickly, the vets were immediately with him but he was passing very quickly,” Given said.
He said all horses were subject to a standard pre-race examination in the morning before the race.
“[Envoi Allen] had his heart listened to, he was trotted up, his limbs were checked. Everything was normal as you’d expect,” he said.