The families of two students from York who were on holiday in Thailand at the time of the tsunami say they have not heard from them since Christmas Day.
The couple had been having a "fantastic holiday"
Sarah Emily Bent, 19 and her boyfriend Robert William Rowbottom, 21, were staying at a resort in Koh Phi Phi.
Miss Bent, who is studying at Northumbria University, had flown to Thailand on 9 December to spend Christmas with Mr Rowbottom.
Their families said the pair had been having a "fantastic holiday".
Miss Bent had been a pupil at Tadcaster Grammar School and Queen Margaret's School in Escrick.
Mr Rowbottom, a former pupil at St Peter's School in York, recently graduated from Newcastle University and was travelling around South East Asia.
A statement released by their families said: "Sarah flew out to Bangkok to spend Christmas and New Year with him before flying back from Singapore on 1 January to resume her studies.
"Robert was flying onto Australia. Both families have been helping each other and have also appreciated the help and support from Australian friends Scott and Sue Wilson and their family who live in Bangkok.
"Sue and Scott were staying on Koh Lanta and survived the tsunami and since then have been tireless in their efforts to find Sarah and Robert."
Meanwhile, a family from York have told how they struggled to survive rising sea waters in the Maldives.
Emily Gibbons, 15, who goes to the Mount School, in York, suffered a slashed thigh, cuts and bruises, after she used all her strength to kick down the
Her twin sisters Hannah and Steph, 17, mum and dad Tony and Deb, both 44, and Mrs Gibbons's mother, Margaret Cowley, 75, survived after being
overcome by rising sea water.