Two women police officers were attacked by a gang as they tried to make arrests following a car crash.
It happened after a Nissan collided with a parked car in High Street, Brighouse at 2100 BST on Sunday.
Two people in the Nissan fled, but as the officers started to handcuff two passengers they were set upon by about 10 people who arrived in two cars.
The two passengers escaped, one still in handcuffs. The officers were treated in hospital for cuts and bruises.
When police reinforcements arrived, a gun, a knife and money were found at the scene.
Officers are now investigating possible links with a robbery in Brighouse earlier in the evening.