A nine-year-old boy has been airlifted to hospital after he was stabbed in a skate park.
West Yorkshire Police said the incident happened at around 4.40pm on Monday at the Carnegie Skate Park in Shipley.
He is now in a stable condition at Leeds General Infirmary.
Officers are looking for a white man aged in his 20s who was wearing a cap and glasses. He is also believed to have a walking stick.
A police spokesman said: "A nine-year-boy received chest and arm injuries and was transported to Leeds General Infirmary via air ambulance."
He added: "This is being treated as a critical incident and numerous resources have been deployed to the scene.
"Inquiries, however; are fast moving and at an early stage."