A 29-year-old man is critically ill in hospital after he was attacked in Huddersfield.
The man, who has not been named, was discovered badly injured with serious head injuries on Blacker Road in Birkby at 8.10pm last night.
The scene was still sealed off today while police forensics experts carried out a detailed search for clues.
A police spokesman confirmed this morning that three teenagers aged 15, 16 and 17 and a 30-year-old man have been arrested in connection with the inquiry and are being questioned by detectives.
The injured man is in a specialist unit at Leeds General Infirmary.