An extensive search by UK Coastguard helicopters centered around the Irish Sea and the Snowdonia area for a missing helicopter has been called off for the night due to poor visibility.
There were five people on board the helicopter, which was flying from Milton Keynes to Dublin.
North Wales Police have taken over the search operation and have called in Mountain Rescue Teams to continue the land based search in the Snowdonia area.
The privately-owned twin squirrel red helicopter is believed to have left Milton Keynes en route to Dublin, via Caernarfon Bay.
A Coastguard spokesman said radar contact with the helicopter was lost this afternoon and the Coastguard was notified to start a search operation at 4.15pm.
A Mayday relay broadcast has been issued to all vessels passing through the Irish Sea route to contact the Coastguard if they have seen anything.
BBC Wales reported that thermal imaging equipment was earlier being used in the search for the missing helicopter.
The Irish Coastguard said they have been asked to assist with a communications search but that the operation in the Irish Sea is being co-ordinated by the UK Coastguard.
UK Coastguard duty commander Peter Davies earlier said a "search plan between Caernarfon Bay and the shore of Dublin" had been established.
He appealed to vessels that were in the vicinity of the Irish Sea and to the public to contact 999 and ask for the Coastguard if they had seen a twin squirrel red helicopter.