A man and woman have been arrested on suspicion of murder after a baby was found unresponsive on a bus.
Police were called by paramedics after the three-month-old girl was found on the bus at 10.20am on Wednesday at the junction of High Street and Carpenters Road in Stratford, east London, Scotland Yard said.
The child was taken to hospital where she was pronounced dead.
A 27-year-old woman was arrested at the hospital and a 52-year-old man was detained at an address in east London later on Wednesday.
The pair are being held in custody at separate police stations.
The girl has not been formally identified and a post-mortem examination will take place on Friday.
Detective Chief Inspector Gary Holmes said: "The death of any child is tragic and we would appeal for anyone with information to please come forward as soon as possible to help with our inquiries."
Anyone with information is asked to call police on 020 8345 1570 or Crimestoppers on 0800 555 111.