Searches are under way for a sailor on a solo challenge who was due to arrive in Baltimore, Co Cork seven days ago.
The UK Coast Guard said the sailboat, 'The Minke', left Plymouth on 18 June and has not made contact since then. It was expected to reach Baltimore Haven by 22 June.
The skipper Duncan Lougee was taking part in the Jester Challenge with a plan to sail the route via the Isles of Scilly, the event organisers said.
The UK Coast Guard said it was leading the search for the 25ft fibreglass folkboat with the help of the Irish Coast Guard, UK police and the RNLI.
The organisers of the Jester Challenge released a statement on their website on 25 June, saying all other yachts and skippers had either arrived at Baltimore or another port of their choice, but that Mr Lougee and the Minke's whereabouts were unknown.
"Everyone involved in the search for Duncan and Minke is perplexed by the absence of any sign of her position," the organisers said, adding that conditions in the Celtic Sea have generally been benign throughout the last week.
The Department of Transport said the Irish Coast Guard is collaborating with the UK MCA [Maritime and Coastguard Agency] with a request for any sightings or reports of the yacht.
"The Coast Guard is conducting helicopter searches, making local enquiries and broadcasting marine VHF messages, seeking any reports on sightings of the vessel," the department said.
However, there have been no reports or information on the vessel being sighted in Irish waters.
The operation was ongoing, it said.
Mr Lougee had both an emergency position-indicating beacon and a personal locator beacon, neither of which had been activated, the Jester Challenge organisers said.
"Hope has not yet been lost that after some major setback, Duncan is still trying to reach a safe haven."
