Four men who travelled on the same train as a teenage girl just before she went missing have been asked to come forward to police.
Police have released CCTV from Ipswich Station
Natasha Coombs, 17, has not been seen since boarding a train to her home in Dovercourt, Essex, from Ipswich, Suffolk, on 27 July.
Police said three men in suits and a smartly-dressed man with a briefcase are believed to have been on the train.
Ch Insp Steve Robinson of Essex Police urged the men to come forward.
Police believe Natasha got off the train at Manningtree, Essex, and have traced her mobile phone signal to the area.
Mr Robinson said: "We know she was looking forward to going out on that Friday night.
"We know at some point in the evening she became upset. The suggestion is she became upset about the situation with her boyfriend."
He said officers are investigating whether Natasha had ordered a taxi to take her home from the train station.
Her grandparents Peter and Wendy Clackett, of Harwich, Essex, have put up their life savings as reward.
They refused to disclose the exact amount but said it was "thousands of pounds".