They were destined for Spain before Revenue officers spotted them.
The DSPCA is minding 12 greyhounds which were seized in Dublin Port over the weekend.
The charity says they were caged in a vehicle with no food or water, and ten of them had muzzles on.
It claims each dog has minor injuries, higher temperatures and are showing signs of dehydration.
It's thought that they would have been travelling for over 24 hours before arriving at their Spanish destination.
Paperwork shows that all dogs are registered with the Irish Greyhound Stud Book and originate from dog trainers in Cork, Kerry, Tipperary and Wexford.
Records also show that nine of the 12 dogs have raced in the last month, one raced last in 2016 and two have no race records recorded.
The Irish Greyhound Board has issued a statement after hearing the news.
It says it's welfare department has begun a full investigation.
The statement reads ;"The IGB condemns any mistreatment of greyhounds in the highest possible terms. Any person or persons found to have been in breach of the Welfare of Greyhounds Act 2011 have been and will continue to be subject to prosecution."
