A search was continuing on Monday evening for a person missing from a ferry in the Irish Sea.Coast Guard Helicopter 116 was involved in the search while the RNLI lifeboat from Dún Laoghaire was also assisting, having taken over from the Howth lifeboat.The search is centred on an area about 40km east of the Baily lighthouse at Howth Head, but the operation is being co-ordinated by the UK Coast Guard at Holyhead.The alarm was initially raised on Monday morning. The Department of Transport said on Monday evening that the search was ongoing.