SEARCHES are continuing for missing three-year-old Mikaeel Kular who vanished from his home in Edinburgh after being put to bed on Wednesday night.
Fears are growing as the little boy has now been missing for over 36 hours.
Police said they are "deeply concerned" as they made a fresh appeal for help in finding him.
Family members were joined by neighbours and emergency services as they searched through the night for him as temperatures plunged to just above freezing.
Police superintendent Liz McAinsh said: "We are obviously deeply concerned that we have had no sightings of Mikaeel. All lines of inquiry in the investigation remain open."
Supt McAinsh said officers were keeping an open mind about why Mikaeel had disappeared and she added: "I remain optimistic, I really do, but as time passes we become deeply concerned."
The boy's mother has been named locally as Rosdeep Kular (33).
Ms McAinsh said: "Mikaeel's mother is getting a lot of support from both the police, her family and her friends but clearly she is very distraught, she just wants her little boy back home with his brothers and sisters. We are very concerned for her."
She said that officers have spoken to Mikaeel's father and that all of the boy's family have been very helpful to the police.
She added: "No one is detained, no one is a suspect, we have no evidence of any criminality."
CCTV from the scene has been examined but has turned up "nothing significant" so far, she said.
She added: "We have spoken to his father. All of his family have been very, very helpful to the police. They continue to help us with our inquiries and obviously we are keen to get as much information as we can from them as we just never know who might hold that vital bit of information that will help us find him."
Mikaeel's mother put him to bed at around 9pm on Wednesday only to find his room empty when she checked at about 7.15am yesterday.
The little boy, who has two sisters and two brothers, usually sleeps in the same room as his twin sister but was alone on Wednesday night.
His jacket and shoes were missing and police are looking into whether he might have left of his own accord.
Mikaeel is slim, 3ft, of Asian appearance and possibly wearing a thigh-length beige hooded coat.
He may also be wearing black gloves with multi-coloured fingers, dark navy blue jogging bottoms, a grey pyjama top with an embroidered turquoise dinosaur on the chest and brown Clarks shoes.
He has a faded scar on the bridge of his nose and a sore on the left hand side of his mouth.
Police issued a new photograph of the boy, showing him in the beige jacket he was believed to be wearing when he disappeared. Supt McAinsh said there has been a "fantastic" response from the public.