Detectives investigating the murder of a gap year student in south-west London want speak to a two people who they feel may have vital evidence.
Police want to trace these two
The man and woman were on the 111 bus before the one that Marsha McDonnell took on her journey home to Hampton just after midnight on 4 February.
Police have said the pair got on the bus at the traffic lights when the bus was in the special bus slip road between the Cromwell Road bus garage and Kingston Station stops at 2345 GMT.
Detectives added that two passengers on the same bus as Miss McDonnell, who they were keen to speak to, have now come forward.
Miss McDonnell was just yards from her family home when she was clubbed over the head three times with a blunt instrument, possibly a hammer.
CCTV footage shows she was not followed when she got off the bus to walk back to Priory Road after a night out in Kingston.
No motive has been found for her murder as she was not sexually assaulted or robbed.
Since news of her death, police have been contacted by the family of a 17-year-old girl who woke up in hospital with head injuries after walking home in nearby Strawberry Hill on 8 January.
She does not remember what happened and it was first assumed she had slipped on ice.
But a pathologist has confirmed she could have been hit over the head and there are fears she could have been the first victim of Miss McDonnell's murderer.