Police have named the 11-year-old boy who died after being hit by a tractor at a farm in Rothwell as Harry Whitlam, from the Wakefield area.
The tractor driver a, 48-year-old local man, was arrested on suspicion of drink driving and causing death by dangerous driving.
Detective Superintendent Scott Wood, of West Yorkshire Police, said: "We are continuing to investigate what has been a tragic incident with the Health and Safety Executive and are still appealing for witnesses to what occurred yesterday.
"Anyone who witnessed the incident is asked to contact West Yorkshire Police Major Collision Enquiry Team on 01924 293047 or via 101."
More top news
Some cloud around but not too chilly!
A man has been given a three-year prison sentence, suspended for two years, for sexually abusing a child in Doncaster in the 1960s.
Over £19k has been raised in 24 hours to repair seven vintage rail carriages that were vandalised in Pickering at the weekend.