A man suffered life-threatening injuries in an attack in Baildon early today.
West Yorkshire Police said the 25-year-old was taken to Bradford Royal Infirmary where he was in a "serious but stable" condition after the incident in Baildon Road shortly after 1.15am.
Police carried out a major investigation at the scene and the road was sealed off between the Station Road and Temple Rhydding Drive junctions until about midday.
Detectives want to trace a male driver of a dark blue or black old-style Vauxhall Vectra who stopped at the scene.
Detective Inspector Peter Craig described him as white, in his early 20s, wearing a green shirt and blue jeans.
"This man stopped and spoke to a couple of witnesses and was also there when the ambulance arrived," said Det Insp Craig.
"It is believed this witness does hold some important information about the offence. We would like to identify who he is and urge him to come forward so we can speak to him."
The man, or anyone else with information about the incident, should contact Airedale and North Bradford CID on 0845 6060606.
A 28-year-old man and a 17-year-old youth have been arrested by investigating officers and were due to be questioned by detectives later today.
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