Suffolk Police have released CCTV footage showing Noah Woods in a Suffolk playground – about half an hour before he disappeared on Tuesday at about 15:00 BST.
The three-year-old, who is partially deaf and non-verbal, was with a relative in Brantham before he went missing, Suffolk Police say.
He is unlikely to respond to his name being called, police added.
The short video shows Noah running around the park.
Police asked residents to review CCTV or doorbell cameras, and for motorists travelling in and around Brantham to review any dashcam footage from 15:00 on Tuesday.
