People living in some areas of Norwich woke up this morning with no power in their homes.
The problem started shortly before 6.30am, when a fault on a high voltage overhead electricity line caused 150 homes to lose power.
UK Power Networks said it had sent engineers to investigate and fix the problem, and they arrived on site at 7.47am.
The postcodes affected are NR1, NR1 1, NR10 4, NR13 3, NR13 4 and NR13 6, though not everyone living in these areas will be without electricity.
Areas hit include the Riverside area of Norwich, the Blofield and Acle area east of the city and Reepham to the north west.
UK Power Networks had hoped to restore supply to all affected homes and businesses by 9am, but this has now been pushed back by three and a half hours.
A statement from the utility firm said its engineers will "work as quickly as is safely possible to get your power back on".
The message said: "Our engineers have been in contact with us to let us know that they need assistance to help remove a tree branch form our overhead network.
"To allow for more resources to arrive and give them time to do this safely, the estimated timeframe to restore your power is now between 11:30am and 12:30pm.
"We're sorry this is taking longer than expected, and we'll continue to keep you up to date, but if any change to this time comes in from our staff I'll let you know as soon as we hear."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here