Mr. Eric Gaisie, the Administrator, confirmed this to the Ghana News Agency and said there were 18 of them.
They were allowed to go home after thorough observation and treatment.
One other person, who sustained gunshot wounds, was however, transferred to the 37 Military Hospital for treatment.
The incident occurred in the residence of the candidate of the National Democratic Congress (NDC), Mr. Kwasi Delali Brempong at Bawaleshie.
Ms Lydia Seyram Alhassan, the ruling New Patriotic Party (NPP) candidate, won the by-election.
The parliamentary seat became vacant following the death of the MP, Mr Emmanuel Kyerematen Agarko.