The state's Corruption and Crime Commission has not named the officer but it is understood to be Cameron Blaine.
The CCC said it had stood down a senior detective after a joint and continuing investigation with police into alleged misconduct.
The man is understood to be Detective Senior Sergeant Blaine, who was captured on video asking Cleo Smith what her name was after the young girl was rescued in the remote town of Carnarvon last year.
"Oversight of police conduct is an integral part of the Corruption and Crime Commission's work and accounts for a significant amount of allegations it receives," the CCC said in a statement.
"The investigation is ongoing and for that reason, the Corruption and Crime Commission and WA Police Force will be making no further comment at this time."
Detective Senior Sergeant Blaine led the search for four-year-old Cleo Smith after her kidnapping in October 2021.
She was found on November 4.
He was one of four detectives who found her locked in a Carnarvon house on November 4 and was the officer who asked her name after she was rescued.
Terence Kelly pleaded guilty to kidnapping Cleo Smith earlier this year and could face up to 20 years in prison.
He is due to be sentenced in December.
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