Yafee was last seen around 5pm yesterday (December 4) in Khartoum Road – off the Barking Road just south of Plaistow Park – and has not been seen since.
Officers are worried he could be out in icy temperatures wearing just his school uniform as friends, family and police try to find him.
Detective Inspector Sam Lockstone said: “With every hour that passes since Yafee was last seen, we are becoming increasingly worried.
“This disappearance is entirely out of character and on what is a very cold night he is potentially alone on the streets of east London in his school uniform with no phone or other means to seek help.
“I’m appealing to anyone who has been in the area in recent hours and who thinks they may have seen Yafee to come forward immediately.
“Your information could be vital to help us focus our search.
“I’m also appealing to those people who are up and about at this hour – the cab and bus drivers, people doing deliveries or those travelling home from the night shift or travelling in for an early start.
“Please keep your eyes open for any sign of Yafee.
“If you see someone who you think might be him, even if you’re not certain, please call us immediately.
“Our priority is finding Yafee, making sure he is safe and well and getting him home to his family who are very worried about him.”
Yafee is described as being of Asian appearance with brown hair and is around 5ft 4in in height, with a medium build.
When he was last seen he was wearing a school uniform of a black blazer and trousers with a black and yellow tie, and carrying a black Nike rucksack.
Anyone who sees Yafee should call 999 immediately, giving the reference 7098/04DEC.
Anyone with other information about his whereabouts should call 101, providing the same reference.
