Police have been informed about potential sabotage on a newbuilding at Flensburger Shipyard in Germany.
The Flensburger Tageblatt website cites an unnamed yard spokesman as confirming it has contacted the authorities on suspicion of "manipulation" on Irish Ferries' 50,000-gt WB Yeats.
Further details were not being disclosed, but the newspaper reported that a valve in the ferry cooling system had been deliberately closed, which resulted in one of the four main engines running hot.
Employees told management of the incident in the middle of October.
The ferry had already been delayed from June to September due to a wait for interior components for public areas and on the electrical system installation in the hull and deckhouse.
The ship is undergoing sea trials and will eventually sail between Ireland and France.
