Published Sunday, 17 March 2013
Police issued separate appeals for Kieran McKeon and Alexandra O'Brien. (© PSNI)
Foyle Search and Rescue carried out searches from Greencastle towards the New Buildings area of Londonderry on Sunday, with the assistance of the Irish coastguards.
They also had help from the civil air patrol, Skywatch, which was used to search areas not easily accessible by crews.
"All the efforts today were unsuccessful and the searches finished at 2pm, and will resume tomorrow morning at 6.30am," Craig Smyth from the rescue team explained.
"We hope everyday that we may come over something, even to find out if the person is in river, or to recover a body."
Searches continue for Kieran after the body of a woman was recovered from the River Foyle on Thursday evening.
Kieran is believed to have travelled to Derry with 21-year-old Alexandra O'Brien.
Alexandra, who was considered vulnerable, went missing from a Dublin hospital last Wednesday.
Police in Derry began searching the river area after personal belongings were found on the Foyle Bridge on Thursday morning.
They have appealed for information that may help find the teenager.
The young man is described as being around 5ft 6ins tall and of slim build, with long brown hair covering his face. When last seen, he was wearing a dark hooded top and grey tracksuit bottoms.