Two more horses died at the Aintree Festival following falls in a race run over the fences used for the grueling Grand National Steeplechase, taking the total for the week to four deaths.
Gullinbursti and Minella Reception died because of injuries sustained in falls in the Topham Chase on Friday, the British Horseracing Authority said.
On Thursday, Clonbanan Lad and Marasonnien died after being pulled up by their jockeys in the Fox Hunters' Chase - also run on the Grand National course - and later collapsing. Neither of those horses was injured by a fall, the BHA said.
''We'd like to express our sympathies to the connections of Gullinbursti and Minella Reception,'' said John Baker, northwest regional director for Aintree's owners, Jockey Club Racecourses.
''While you can't remove all risk from any sport, we acted on evidence to make significant changes here at Aintree, including to the cores of every fence on the Grand National Course, and we've seen hundreds of horses compete safely since over the last few years.''
Earlier, the biggest favorite of the festival proved a big disappointment.
Vautour - a 1-5 shot ridden by leading jockey Ruby Walsh - fell while leading the Melling Chase, allowing God's Own to take a surprise win in the day's feature race.
Vautour landed steeply after jumping the ninth fence and fell in the biggest shock of the festival so far. God's Own benefited by beating Al Ferof to the winning post at odds of 10-1.
Walsh also fell from Blood Cotil in the Topham Chase and did not take up his mounts in the following two races. He has sustained a hairline fracture to his wrist and will not ride Sir Des Champs in the Grand National, the world's toughest steeplechase, on Saturday.
That ride goes to Nina Carberry, a leading female amateur jockey.
Vautour's fall was a major blow for Irish trainer Willie Mullins, who is vying with Paul Nicholls to be the champion trainer in British racing with two weeks left in the jumps season.