Fimber, 14, was killed after an incident at Carr Gate police headquarters near Wakefield on 15 October last year.
CCTV footage showed the horse, who had been with the force for 11 years, looking “spooked” in the paddock before vaulting a fence and colliding with a wooden post.
In the days after the incident, police appealed to the owner of a radio-controlled drone found nearby to come forward.
The drone was a widely-available model, the Walkera Runner 250. Measuring about nine inches (27cm) long, they cost about £200.
Police said at the time that Fimber, who was used to the a helicopter taking off and landing nearby, reacted to the drone landing nearby or close to him, causing him to be spooked.
In a statement issued this week, Detective Superintendant Simon Atkinson of West Yorkshire Police said: “Detectives did conduct a full investigation into the death of Fimber but despite a number of enquiries, were unable to identify the owner of the drone.”
He added: “Officers concluded it was more than likely that the presence of the drone spooked Fimber, who was an experienced police horse.”
“Following enquires and a media appeal regarding this incident, it was determined there were no further lines of investigation, resulting in the matter being finalised. If any further information comes to light it will be reviewed.”
Mr Atkinson said in the days after Fimber’s death: “I appreciate that radio-controlled drones are becoming increasingly popular and I am not wanting to detract from the pleasure people get from flying them,” he added.