Hampshire Constabulary has issued the alert on behalf of Thames Valley Police in a bid to find missing 16-year-old Lenny Holden.
The teenager was last seen in Howth Drive, Woodley, at 7.10am yesterday getting into a taxi.
Officers say the youngster is ‘known to frequent Portsmouth and may be travelling to that area’.
Lenny is described as white, around 5ft 2ins tall of stocky build with short brown hair.
He was last seen wearing a grey tracksuit but is not believed to have taken any belongings with him.
He is also known to frequent Portsmouth and may be travelling to that area.
Investigating officer Inspector Nicky Hamblin, based at Reading police station, said: ‘We are concerned for Lenny’s welfare and would appeal to anybody who knows of his whereabouts or believe that they have seen him to please get in touch with Thames Valley Police by calling 101, quoting reference number 43210377857.
‘Similarly, if you see him, please call us on 999.
‘Lenny, if you see this appeal, please get in touch with us, we want to know that you are safe and would ask you to contact us.’