Fiji's Public Prosecutor will now decide if charges should be laid against opposition MP Pio Tikoduadua following his release from police custody last night.
The National Federation Party president was arrested at his home early Tuesday over a video he posted on social media.
The chief of intelligence, Biu Matavou, said police had completed their investigation into Mr Tikoduadua.
Mr Matavou said the case file had been submitted to the Office of the Director of Public Prosecutions for independent legal advice.
NFP leader Biman Prasad condemned the arrest and said the heavy-handed tactics of police were uncalled for.
Mr Prasad claimed police were upset about a video on Mr Tikoduadua's Facebook page where he set out allegations of police brutality in a village in Tailevu.
He said the incident had received wide publicity.
Earlier Police Commissioner Sitiveni Qiliho said police officers were being investigated over the alleged assault.
Mr Qiliho said he had directed the Criminal Investigations Department and the Internal Affairs to carry out simultaneous investigations into the alleged incident.
The commissioner also said he would ensure the investigations were conducted thoroughly and promptly.