Sheikh Mohammed bin Rashid Al Maktoum has launched an internal investigation into his equine operations after an illegal shipment of unlicensed veterinary goods was seized from a Dubai government private jet by UK authorities at Stansted airport in May.

Thousands of pounds worth of unlicensed products – including steroidal injections, anaesthetics and anti-inflammatories that have been described as “potentially toxic and dangerous to horses” – were seized and destroyed by the UK Border Agency and the Veterinary Medicines Directorate (VMD) on May 3rd at 7pm, following the arrival of a Dubai Royal Air Wing flight.

Sheikh Mohammed is owner of the UK’s largets Flat racing operation Godolphin and monarch of the gulf emirate. Her Highness Princess Haya, his junior wife and president of the International Federation for Equestrian Sports, has been ordered to conduct a thorough investigation into the seizure at the airport and a separate raid by the VMD last month at Moorley Farm in Newmarket, a location owned by his Darley Management operation, where a number of similar products were found.

The Guardian understands Sheikh Mohammed is extremely concerned at the development which comes only months after his Godolphin thoroughbred operation was rocked by the biggest doping scandal in racing history.

The shipment seized at Stansted, reportedly labelled incorrectly as “horse tack”, did not include any anabolic steroids. However, there were significant quantities of goods understood to be for use on endurance horses and the VMD, in conjunction with the Royal College of Veterinary Surgeons, is investigating the matter. A full inventory of the seized products has been seen by the Guardian and forwarded to Godolphin and the British Horseracing Authority (BHA). Neither would confirm its accuracy.

A spokesman for Princess Haya told the Guardian: “Nobody seems to know in the organisation who is buying what or where. That’s one of the reforms that they want in place. We’re trying to find out what happened, why it happened and to make sure it doesn’t happen again.”

Keith Chandler, president of the British Equine Veterinary Association, said some of the products seized were potentially dangerous to horses and should be “kept under lock and key in a safe”, while the VMD stated the medicines “were not authorised in the UK and had not been imported in accordance with the regulations”.

Chandler said: “Some of these medicines are not only toxic if they are misused but they are potentially dangerous to the horses. They really are medicines that should not be on the premises of any horse owner, no matter how experienced.

“They definitely should not, under absolutely no circumstances whatsoever, be found on an owner’s premises. There are powerful sedatives and anaesthetics on the list, there are powerful painkillers and one of the products is toxic and dangerous to humans as well. They are clearly being used to treat and medicate horses.”

Among the products seized at Stansted were 100 Tildren injections, a substance that is used by vets for horses with bone problems. “This is not just a matter of importing a few horse warmers, this was a considerable operation in terms of importing medicines,” Chandler said. “These medicines should be kept under lock and key in a safe.”

Princess Haya’s spokesman insisted Sheikh Mohammed was unaware of the presence of the pharmaceuticals on the flight from Dubai or the raid at Moorley Farm until now. “I can assure you that Sheikh Mohammed was not aware of any such products in the cargo of any Dubai Royal Air Wing flight into Stansted on that date,” he said.

It is the second time this year that his operations have been engulfed in controversy. In April the disgraced former Godolphin trainer Mahmood al-Zarooni was banned for eight years by the BHA after using anabolic steroids on 22 racehorses at Moulton Paddocks in Newmarket. The BHA insists the Stansted seizure was not related to racing, citing assurances given by the VMD.

Sheikh Mohammed said he was “appalled and angered” by Zarooni’s actions, with a swiftly completed BHA report declaring that the trainer acted “autonomously” and that the doping programme was the work of a rogue individual rather than a collective operation.

Princess Haya, who will step down as president of the FEI in November 2014 after the conclusion of her second four-year term in the role, sent out a directive on September 12th to the major components of Sheikh Mohammed’s equine operation, including Darley and Godolphin, to establish a centralised auditing system in order to maintain control over the purchase and movement of veterinary goods.

On Tuesday she will meet Lord Stevens, the former Metropolitan police chief who also headed the FEI Clean Sport Commission, to discuss her investigation.

On August 7th the VMD, an agency within the government’s Department for Environment, Food and Rural Affairs, seized 124 products from Moorley Farm in Newmarket. Jaume Punti Dachs, a Spanish endurance trainer based at the stable who has trained horses for Sheikh Mohammed and is also a member of the FEI endurance committee, said there was no “wilful or careless wrongdoing at his yard” and that the products were “all substances you can buy in the UK”.

However, in a directive seen by the Guardian, Princess Haya has called on all individuals at various organisations within the hierarchy of Sheikh Mohammed’s endurance and racing structure “to ensure that there is no breach of regulations”.

She wrote: “I wish for all managers to accept the responsibilities that their position bestows on them and to ensure that all efforts are made to protect the good name of the Maktoum family at all times.”

Michele Verroken, the director of Sporting Integrity and former head of ethics at UK Anti-Doping, believes Princess Haya must find out which members of the Sheikh’s organisation were responsible for the infringement and “hold them accountable”.

She said: “This reminds us that continued vigilance to counter illegal importation is essential to prevent sport being corrupted. Customs and border agencies make a major contribution to the enforcement of sports’ rules as well as national laws.

“As president of the FEI, Princess Haya, has an important role to pursue the truth, to find who is responsible and to hold them accountable.”

The BHA insists there is no link between the seizure at either Stansted or Moorley Farm and the racing industry.

Adam Brickell, the BHA’s director of integrity, legal and risk, said: “The BHA was notified of the seizure of veterinary care products, some of which are not licensed for use in the UK. Defra have confirmed to the BHA that they consider there to be no link between the seizure and the racing industry and that the products were not intended for use on thoroughbreds.”

Guardian Service