The investigation committee has primarily found that a youth was tortured at Barishal district office of Narcotics Control Department.
Preparation to take disciplinary action is underway, said Paritosh Kumar Kundu, additional director and head of the investigation team.
"We have found evidence of beating of Maruf Sikder by Inspector Abdul Malek Hawlader on the ground floor of the narcotics office on September 22 last year," the official said.
"The incident happened five months ago. Someone close to Inspector Malek might have recorded the video of torturing the youth. However, we initially found the truth about the incident," he added.
The investigation of giving yaba tablets to him is still ongoing, he said, adding the victim Maruf Sikder secured bail 19 days after his detention and he is now out of jail.
Maruf Sikder (20), a resident of Barishal city, was picked up by Malek on September 22.
Later he was taken to the office and beaten, and five yaba tablets were given to him in order to take confessional statement, he alleged.
Maruf, who was accused of three cases, said he used to work as a fourth-class employee in a local newspaper office. But now he is unemployed due to the coronavirus pandemic.
Inspector Abdul Malek Hawlader of Barishal District Office of the Narcotics Control Department said that he was only interrogating Maruf in the drug related case.
Yaba was recovered from his possession and the allegation of giving yaba to him is false, the inspector added.