More than 70 police officers are now investigating how a teenager came to be unconcsious on a Ramsgate street.

They are probing whether an incident in which the 17-year-old was knocked unconscious and robbed, suffering serious head injuries, is linked to two other robberies in the same town.

It comes as Sam Eastwell's mother made an emotional plea for information, saying: "My family cannot believe that Sam has suffered such injuries in an area we love and in which Sam has lived all of his life."

~Listen: Hear Det Insp Andy Summerfield tell of the major police operation to find the culprits

Her son, who is waiting for his A-level exam results, was found by a passer-by in Albion Place, Ramsgate, at 2.15am Thursday.

He has since undergone two operations and been placed on a life support machine in a London hospital, where his condition is described as "critical".

The teenager's gold sovereign ring and gold knotted ring, black Samsung Soul mobile phone and Samsung Touch MP3 player are all missing. A wallet taken from him has now been recovered.

Sharon Eastwell said: "Sam is a hard working, sporty and very outgoing teenager who has aspirations to become a police officer in the future. He's a very popular young man and he has a very large and close circle of friends."

Police are still not certain how Sam suffered his injuries - but say the incident could be linked to robberies involving two hooded youths, the first in Newington Road on Wednesday evening and the second in Victoria Parade less than an hour before the Albion Place incident.

A watch, mobile phones and cash were among the items stolen.

The offenders in the Victoria Parade incident are described as white, aged about 18 or 19, between 5ft 10ins and 6ft, both slim, but one heavier built than the other.

One was wearing a yellow and grey striped hooded top and dark jogging bottoms. The other was wearing a white or light-coloured hooded top and dark bottoms.