One man has been released without charge by gardaí investigating events around the detention of bulk cargo vessel MV Matthew.
Five people are now in custody at garda stations in the south as part of the investigation.
The Panamanian-registered ship, which left South America last month, was intercepted and escorted to port in Cork on Tuesday by an Irish joint task force which included gardaí, the naval service, army rangers and Revenue customs.
It is thought the ship was intending to rendezvous with a trawler which ran aground off the Wexford coast.
Two other men are before the courts in connection with the investigation.
Earlier today an eighth arrest was made as part of the investigation for alleged organised crime offences.
