UK Power Networks estimates some 369 homes in Norwich are without electricity.
NR2 1, NR2 2, NR2 3, NR2 4 postcodes have all been impacted.
A spokesman for UK Power Networks said: “Our engineers are on their way. We believe the issue is on our underground network that initially interrupted power to 2431 properties.
“However, we have managed to divert power back to some properties, so 369 properties are still affected.
“Specialist engineers from our control room will continue to divert power remotely, so your power may come back on at any point.
“Sometimes we can’t restore everyone this way, so we’re also sending staff to check our equipment.”
It is estimated that the issue will be resolved between 5.30pm and 6.30pm.