The other horses involved in this "precautionary measure" are those deemed to have been in contact with the horse that died after being stabled in the same area since March 22, including those who had already left the venue.

Those responsible and their National Federations and national head vets have all been notified.

The FEI has given an update on the situation, and measures taken by the FEI, "in consultation with the Organising Committee and the Belgian National Federation".

The update reads: "The affected horse, which had already left the venue, presented neurological signs for EHV-1 upon returning home which were subsequently confirmed through an EHV-1 test.

"The horse unfortunately died on 31 March and the FEI is following up on the circumstances of the horse’s death.

"All blocked horses have been isolated and will be prevented from attending any FEI events until they have fulfilled certain health requirements which are imposed in order to minimise any potential transmission of the virus, both to their own horses and the wider horse population."

The horses involved have to comply with all return to competition protocols and have the restriction lifted by the FEI veterinary department.

In most cases, horses exposed to EHV-1 will develop a fever and possibly nasal discharge and then go on to recover, according to the UC Davis Center for Equine Health.

"We are grateful for the community’s vigilance in all matters of biosecurity and once again reiterate the importance of the horse health requirements, and the necessity to fulfil these via the FEI HorseApp to ensure the maximum safety for all horses competing at international events," the spokesman added.

"All information in relation to the horse health requirements is available on the dedicated hub.

"Should you have any questions regarding this matter, don’t hesitate to contact the veterinary department."