Mr Godwin Idemudia, the General Manager, Corporate Communications of the company, said on Monday that the outage which occurred about 2.27 p.m. on Sunday affected Ajah, Akangba and Agbara transmission stations.
According to him, the cause of the system collapse is still unknown.
The general manager, however, assured customers that they would be updated as soon as the company received supply from the Transmission Company of Nigeria (TCN).
Idemudia said gradual restoration of power supply had started.
“Though gradual restoration has commenced but a large part of the network are still without power supply.
“The situation is being monitored and the power restoration will be done as soon as the situation normalises.
“We regret any inconveniences caused by the outage,” he said in a statement.