Police are urgently seeking help identifying a man after the fatal stabbing of nine-year-old Lilia Valutyte, allegedly in front of her sister.
Lincolnshire Police released four CCTV images of the man and warned anyone who sees him not to approach him, but to call 999 immediately.
Police added that two people arrested earlier this week have now been released without further action.
Chief Superintendent Martyn Parker said: “Our officers have been working around the clock on this investigation and the help of the public could prove crucial.”