A teenage girl and two younger children were last seen walking towards Staines town centre just after 3.15pm on Monday.
Three children are missing after a day out at Thorpe Park.
A 14-year-old girl named only as Khandi was with two younger children Amelia, nine, and Malik, seven, at the theme park in Surrey on Monday, but the trio were reported missing at 7pm.
The two younger children are related, Surrey Police said, but gave no further information on why they were with the teenager.
Khandi is black, slim, 160cm tall, and was wearing black or grey jogging bottoms, a white top, white trainers, black framed glasses, and multiple bracelets on each wrist.
Amelia has been described by police as European. She is 110cm tall, slim, and was wearing grey jogging bottoms, a grey long-sleeved top with “Believe” written on it and white trainers.
Malik is European and also 110cm tall, slim and was wearing black jogging bottoms, black trainers, and a green long-sleeved top with stripes.
They were last seen walking away from Thorpe Park towards Staines town centre at around 3.17pm on Monday. It is believed they may have travelled to London.
Anyone who has seen the children or has information about where they might be can call Surrey Police quoting the reference PR/45240068376.
