A man has been arrested in connection with an attack on a police officer who carried out a “routine stop” on a car.
The PC was allegedly assaulted by two men after pulling over the vehicle in Synod Inn, Ceredigion, on Saturday.
Dyfed-Powys Police is carrying out “large scale” searches in Cardigan for the second man after a tip-off.
Ch Supt Peter Roderick asked people to be “vigilant, not fearful”, saying the suspect posed more of a risk to police officers than members of the public.
The force said a 29-year-old man from Sussex has been arrested on suspicion of assaulting a police officer and three counts of taking vehicles without consent. He remains in custody.
Police have described the second man as white and could be wearing shorts and a white T-shirt with grey in the middle.
The police officer who was allegedly assaulted is undergoing medical assessments after suffering cuts and bruises.
He is not yet able to return to work, a force spokeswoman added.
Ch Supt Roderick added: “We continue to urge people in Ceredigion to keep their domestic and farm vehicles locked, with the keys out of the ignition.
“This will minimise opportunities for the individual to leave the area.”