WELLINGTON (Reuters) - Parts of New Zealand’s capital city, Wellington, ground to a halt on Friday after a substation fault cut off power to the nation’s parliament, shut down traffic signals and plunged businesses into darkness.

Utility provider Wellington Electricity said on its website the outage had cut electricity to around 12,500 customers in the north of the city and it was working to fix the problem.

Media company Stuff reported that parliament was in semi-darkness and its internet was down while it relied on back-up generators.

The legislature was not in session on Friday but parliamentary committees and ministerial offices were affected.

Prime Minister Jacinda Ardern was still in Auckland, New Zealand’s largest city, after returning to work the previous day from six weeks of maternity leave. She was set to arrive in the capital on Saturday.

Lectures at Wellington’s Victoria University were canceled and court operations were halted due to the outage, Stuff reported.

Wellington City Council said on its website drivers should hold off on unnecessary travel while some traffic lights were out.