Police have released CCTV images of three brothers who went missing from their foster family after going on a bike ride.
The boys - Remus, 15, Janko, 12, and David Matloch, 10, - took their bikes out on Monday evening (August 11) but didn't return.
Shortly after leaving their foster home in Sunderland at 5.20pm, they were spotted buying a Metro ticket to Newcastle. They had been expected home at 8pm.
They were last seen at Newcastle Central Station after 6pm yesterday without their bikes.
The three brothers had said they had been going on a cycle ride to the nearby Mowbray Park.
Northumbria Police said they were concerned for their welfare because the boys hadn't answered their mobiles phones and had never previously gone missing.
The brothers, who are Polish but speak good English, all had bikes with them and were wearing helmets when they left.
Dark-haired Remus, who has a distinctive quiff, was last seen wearing jogging bottoms and a T-shirt; fair-haired Janko had mustard-coloured chinos with a blue waterproof.
David has shaggy dark brown hair and a chubby build and is possibly wearing shorts and a top and a silver coloured cycling helmet.
The brothers are thought to have family members in Blyth, Northumberland and South Shields.
Officers are appealing for the boys, or anyone who has any information about their whereabouts, to contact them straight away.
Police said the boys were excited about an upcoming holiday this Friday and had very little money and no passports.
CCTV footage showed them entering the Park Lane Metro station around half a mile from their home without their bikes and helmets.
They were later spotted by cameras at Newcastle Central railway station - a 45 minute train journey away.
Superintendent Alan Veitch urged the boys to get in touch and said police would pick them up from any location.
He told a press conference the boys grew up in Blyth, Northumberland, but had lived with foster parents in Sunderland for 18 months.
Remus, Janko and David's mother is believed to be in Poland and their father in Romania, and it is not known if they are aware that they are missing.
Superintendent Veitch said: "We are increasingly concerned for the boys' welfare and we are appealing for anyone who may have seen the youngsters travel on the Metro from Sunderland Park Lane arriving at Newcastle Central Station at 6.04pm on Monday night.
"We urgently need to hear from anyone who saw the boys after that. We don't know if they travelled onward by rail, or if they came into Newcastle, or used another form of transport to go elsewhere.
"So far we believe they may have been travelling to the railway station for a purpose to meet with a friend or family member.
"We would ask if anyone knows the boy's whereabouts we would ask them to contact police straight away."
Anyone with information should contact Northumbria Police on 101, extension 69191, quoting log number 1276 of 11/08/14.