Police have said they need to be “realistic” about future options in the search for missing teenager Liam Smith, last seen 11 days ago.
The 16-year-old was captured on CCTV entering Union Square shopping centre before boarding a 202 Stagecoach Bus at 1.11pm at Aberdeen Bus Station on Saturday November 17.
Officers have received 139 reported sightings of Liam from various locations across the north-east, all of which have been eliminated.
Searches have been focused on Crathes in Aberdeenshire after two credible reports.
This has led members of the public and the force looking over rough terrain in challenging environments as part of efforts to find him.
Chief Inspector Martin Mackay said: “Every available police resource has been dedicated to our search for Liam and it continues to cause us all great concern that he has not yet been found.
“Eleven days is a long time for a teenage boy who has little experience of the outdoors to be missing and as more time passes without seeing or hearing from him, we need to be realistic about the options we have moving forward.
“The terrain we are entering with regard to our searches is extremely challenging – not helped by the current weather – and even our own officers are finding it difficult to navigate certain areas.
“I must stress just how challenging the land is we are dealing with, ranging from dense wooded areas to expanses of water, and we don’t want anyone put in harm’s way.
“Organised public searches can also be very resource and time-intensive to coordinate and our time is extremely precious at the moment.”
It is understood Liam bought a ticket for Raemoir Road in Banchory but a passenger told police they believe he got off at Crathes.
Police Scotland said this was backed up by a “credible” sighting on an estate in the area later that afternoon.
Mr Mackay urged anyone who in Crathes Estate to keep an eye out for any clues of Liam’s locations.
Officers would also like to hear from people who may know why he travelled in the Deeside direction.
Liam is white, around 6ft 4in and of slim build.
He has short brown hair and walks with a distinctive gait.
When last seen he was carrying a camouflage North Face rucksack and was wearing Nike Air Max trainers.
He bought Lucozade, Jaffa Cakes and Dairy Milk at Sainsbury’s before he left Aberdeen.
Mr Mackay added: “I would ask to the public to continue supporting our efforts, which have so far included sharing our social media posts to printing off posters.
“The response to our appeals has been unprecedented and it has not gone unnoticed by Liam’s family nor us.”