The Department of Agriculture has said it is investigating and incident in which 11 greyhounds were discovered dead in a van on board the Irish Ferries Oscar Wilde vessel just before it docked in France on Monday afternoon.

The greyhounds were being transported in cages in the van and it is believed they suffocated during the 14-hour journey from Rosslare to Cherbourg.

An Irish Ferries spokesperson said they were unaware the dogs were being transported in the vehicle.

The driver was questioned by French police but has since been released.

As a precaution, nine other pet owners travelling with their animals were held on board the vessel for a short time after it docked until the cause of the greyhounds’ deaths was established.

In a short statement the Department of Agriculture described the incident as "very serious" and said it is continuing to liaise with French authorities.

Meanwhile, Bord na gCon, which regulates greyhound racing in Ireland, said it was horrified at the deaths of the 11 greyhounds.

The board said it would provide all possible assistance to investigations into the incident by authorities in France and by the Department of Agriculture here to determine whether there has been breach of animal welfare regulations surrounding the transport of animals.