Gardai say their investigations are continuing into a multi-million euro VAT Carousel Fraud.
A man in his 50's was arrested as part of the investigation earlier this week, and was questioned at Castlerea Garda Station under section 50 of the Criminal Justice Act.
Castlerea Gardai have confirmed to Midwest News that the man was released without charge yesterday evening, and a file is being prepared for the Director of Public Prosecutions.
A woman in her 40's had previously been arrested in Co Louth in May in connection with the investigation, and was subsequently released without charge.
The investigation has been ongoing since 2017, and it's claimed the fraud involves the movement, purchase and sale of goods between different companies in the Republic of Ireland and Northern Ireland for a number of years.
Gardai say this type of fraud involves supplier companies, VAT-registered entities, customer companies and transport companies.
The ongoing investigation involves Gardai, the Criminal Assets Bureau, PSNI, National Crime Agency and Her Majesty's Revenue & Customs Agency.