More than 400 people have joined the search for a missing teenager.
Cormac Clare was last seen at his home in Kilteel, Naas, Co Kildare, in the early hours of Monday.
Superintendent Patrick Mangan, of Naas Garda station, appealed to the public for help to trace the whereabouts of the 18-year-old student who had been hitchhiking.
"We have grave concerns for Cormac's welfare and have carried out extensive searches since Monday," he said.
"This morning there are over 400 people, including local gardai, garda divisional search teams, Garda Water Unit, Civil Defence and members of the public from the locality, involved in the search.
"We are especially appealing to members of the public who may have seen Cormac near his home on Monday morning, or hitchhiking on the N7 or N81 routes, to contact us."
Cormac is described as being 6ft 1in or 6ft 2in tall, and thin, with short tight brown hair.
His parents, Seamus and Lorraine, have said his disappearance is totally out of character.
When last seen, he was wearing a navy jacket (possibly Regatta), a wine-coloured hoodie, navy plain Nike track suit legs (cotton style) and runners.
It is possible he also had a small black and green Jack Murphy rucksack in his possession, gardai said.