Electrocution has been blamed on the deaths of two horses at Newbury racecourse over the weekend.

Fenix Two and Marching Song were scheduled to take part in the opening race at Newbury but instead collapsed to their deaths in the paddock. Two other horses, The Merry Giant and Kid Cassidy, are also thought to have received electrical shocks but managed to survive.

Kid Cassidy was withdrawn from the race by trainer Nicky Henderson but the “badly traumatised” The Merry Giant continued as planned, finishing last of the runners. After being delayed by 20 minutes and missing three of its runners, the novice hurdle went ahead and was won by Al Ferof, a contender for Paul Nicholls. All subsequent races at Newbury were cancelled after the event amid fears of further problems for the horses.

Fenix Two’s trainer, Jonjo O’Neill, said: “Kid Cassidy was in front and he took a turn. We thought he was bucking and kicking and he went down on his knees then he seemed to be ok. Mine reared up and we couldn’t get him back, it was like he was stuck to the ground. It was the weirdest thing I’ve ever seen in my life”.

Chairman of Newbury Racecourse, Christopher Spence, said: “It’s a nightmare for everybody. We can’t be certain what it is, we all think it’s electric, but we don’t know”. Investigations into what caused the deaths have been launched by the police, Southern Electric Power Distribution and the British Horseracing Authority.