The PSNI has said organised crime gangs regularly co-operate on a cross-border basis to import and distribute large shipments of drugs.
They were speaking as they put on show £3 million worth of cannabis and cocaine seized at Belfast port at the weekend.
It is one of the biggest single seizures by the authorities in Northern Ireland in recent years.
Detective Inspector Conor Sweeney said while it was too early to be specific about the destination of the seizure - criminals regularly co-operated for profit in similar situations.
"In general, the model we're seeing is absolutely some of it will be going across the border," he said.
Half the drugs were found in a van which had been put in the back of an articulated lorry.
The rest was found in a false bottom of the trailer when it was searched later.
Detective Inspector Sweeney said the profits from the drugs would have been used to fund other criminality including the purchase of guns.
There are estimated to be around 70 organised crime gangs in Northern Ireland alone.
Mr Sweeney said there was regular co-operation with the gardaí to thwart drug trafficking.
Two people were arrested in connection with the £3m seizure - one of them has been charged in connection with the find.
