Ondo Police Command has said the fire outbreak at the Akure office of the Independent National Electoral Commission (INEC) was caused by faulty electrical connection.
It said talks of saboteurs causing the fire were untrue.
Over 5,000 card readers to be used for the October 10 governorship election were razed in the inferno.
The card readers were kept in two containers on the premises of INEC.
Some parties had called for investigation into the incident, to arrest the perpetrators.
Police Commissioner Salami Bolaji said at a news briefing in Akure that the Ondo Fire Service report on the incident had put to rest issues of saboteurs setting containers ablaze.
He said other findings would be made public.
Salami said: “The result of investigation into the incident is out. The fire was caused by faulty electrical connection and the smart card readers were burnt. They were kept in two containers on the premises of INEC and the air conditioners were kept on for 24 hours.
“This will put to rest speculations that the fire was caused by saboteurs. If there are other findings, we will let you know. For now, the major cause is faulty electrical connection.
“This report is final from the fire service. They have the authority to investigate fire incidents in Akure.”
On the reported destruction of campaign posters and banners by political opponents, he said his men were working to arrest the perpetrators.
“We are working hard to curtail political violence. We are meeting political leaders to tell their followers to desist from attacking each other. We are investigating all aspects about the killing in Idanre.”