Revenue officers have seized €647,000 worth of nitrous oxide, commonly known as laughing gas, at Dublin Port.
Officers seized 8,640 canisters with an estimated value of €342,000 on Monday as a result of risk profiling.
The discovery was made in a consignment originating from Hong Kong which had arrived via Rotterdam and was intended for an address in Northern Ireland.
Separately last Thursday, Revenue officers seized 10,800 canisters of nitrous oxide with an estimated value of €305,000.
These were found in a consignment which had arrived from Zeebrugge in Belgium and which was also intended for an address in Northern Ireland.
While this product is legitimately used in the catering industry, Revenue has a range of powers to detain and seize psychoactive substances in instances where there are "reasonable grounds for believing that the goods being imported are not intended to be utilised for legitimate purposes".
Investigations are ongoing.
