Police are searching for a two-year-old and his mother after they failed to return from an agreed outing.
Megan Rescorla, 20, picked up her son Reuben Westmoreland from the care of his father in Bridlington on Saturday morning.
But Ms Rescorla, who is also from Bridlington, failed to return the child to his father by lunchtime as agreed.
Police have been making inquiries since being alerted by Reuben’s family on Sunday.
But they have been unable to trace Ms Rescorla and her son, who are thought to be with her partner Luke Harrison, 21.
Police believe the pair may have taken the child to Bradford where Mr Harrison has contacts.
When his father last saw him, the light-brown haired toddler was wearing blue Nike joggers and a grey Batman coat.
Anyone who can help is urged to call police on 101.