Nine million black market cigarettes seized in Dublin today were bound for the UK market.
The massive haul of illegal 20 packs marked "Benson and Hedges" were stuffed into a container on a ship from China.
It is believed they could have been sold for almost e4m.
The cigarette packets carried UK government health warnings.
A Customs spokeswoman said it could not comment at this stage on whether they were bound for Northern Ireland or Britain.
"For operational reasons we can't comment any further because the investigation is ongoing," she said.
Customs officers using so-called profiling techniques uncovered the huge stash in a cargo container indicating that it contained disposable cups.
The container was on a ship from China delivering cargo to Ireland that docked in the capital this morning.
The seizure was part of an operation targeting the supply and sale of illegal tobacco.