Racing: The British Horseracing Authority's review of the 2012 Grand National found today that the deaths of Synchronised and According To Pete could not have been "foreseen nor prevented."
The report confirmed that Synchronised, who unshipped Tony McCoy on the way to the start, had been given a full veterinary examination before he was allowed to line up and had a heartbeat that registered "barely above a normal resting rate."
Having fallen at Becher's Brook on the first circuit he ran riderless until falling again at the 11th fence, where it appeared he fractured his right hind tibia and fibula.
According To Pete was brought down by a faller at Becher's on the second circuit but was jumped into by another horse as he got up.
The BHA said it was unclear which incident led to the fracture of the horse's left fore humerus.
BHA official Jamie Stier said: "The review into how the two sad fatalities came to occur was conducted using veterinary evidence together with detailed analysis of all available television footage.
"The findings include reference to Synchronised getting loose before the start as it was felt important to establish beyond doubt that this episode played no part in the events that resulted in his injury.
"In the case of both Synchronised and According To Pete, it was apparent that factors one could neither have foreseen nor prevented were prevalent in the events that led to the two horses sustaining their injuries."
Stier also looked into the delayed start and found that all 40 riders had breached the rules.
No disciplinary action will be taken but the jockeys will receive letters detailing the BHA's and Aintree's disappointment over their conduct at the start.
Stier said: "We found that in the course of the three occasions on which the field lined up before the race was under way all 40 riders appeared to be in breach of the rules, in that they either lined up prior to being instructed to do so, or lined up despite being instructed not to do so.
"However, taking into account the mitigating circumstances caused by the delay to the start of the race - firstly Synchronised getting loose which was then compounded by the complications experienced with resetting the starting tape - it has been decided that no disciplinary action will be taken," said the BHA official.
The BHA have not yet decided whether any further changes will be made to the Grand National course.