Mr Maigandi said the incident occurred when the canoe capsized while ferrying the victims across Tindifai River on Monday.
Two policemen were also killed during the incident.
An electric power accident has been reported at the Ikoyi Prison, a major correctional facility in Lagos.
Two village heads, the chairman of a vigilante group and two other persons were killed
Mr Onyema was indicted by a federal grand jury in the United States on November 19.
His kidnap has sparked tension in the Nsukka suburb of Enugu.
The incident occurred at Sabon-Gari Village when the hoodlums laid an ambush along the road.