Officers have released a CCTV image of a man they want to speak to in connection with a robbery at Swinton rail station.
On August 16, a 16-year-old boy was assaulted for his mobile phone while waiting with friends at the station.
DC Lisa Massey said: “While the boy was waiting for his train he was approached by a group of three young men.
“One of the group tried to snatch the boy’s mobile phone – a BlackBerry Curve – but failed to grab hold of it.
“The man then demanded the phone and, when the boy refused to hand it over, the offender became aggressive, sat on the victim and punched him.
“Despite this the boy still refused to hand over his phone, but the offender threatened him again and, fearing for his safety, the victim gave up his phone.
“It is vital that we trace the man from the CCTV. I believe he has vital information in relation to the robbery.”