A man and his daughter have been missing since Tuesday afternoon.
Alexandru Matei, 39, and his two-year-old daughter Antonia, were last seen in Pentewan Gate, Fishermead, at about 1.30pm on Wednesday.
Antonia has a pierced right ear and blond hair. When she was last seen, she was wearing a blue jacket with a pink and blue pattern of butterflies, dark blue sallopettes and brown Ugg boots.
Alexandru is stocky, with short black, greying hair.
When he was last seen, he was wearing a dark blue jacket.
It is possible that Alexandru and Antonia are with two other adults, possibly a man and a woman.
They were last seen in Milton Keynes, but Alexandru has links to Kempston in Bedfordshire.
Detective Chief Inspector Nick Glister said: “I am becoming increasingly concerned about the whereabouts of Alexandru and his two-year-old daughter Antonia, who were last seen this afternoon.
“However, I want to reassure the local community that we are conducting an extensive investigation to find Alexandru and Antonia.
“I am making this public appeal because there might be people out there who have information that can help our enquiries.
“If anyone thinks they have seen Alexandru or Antonia, or have any information as to their whereabouts I would urge them to please contact police immediately.
“In an emergency call 999, or a non-emergency call 101, quoting the investigation number 609 (5/12).”