London (CNN) Trains ground to a halt, homes went dark and cars wandered through intersections without functioning traffic lights as large swathes of London and southern England temporarily lost power Friday.

All power has now been restored, according to UK Power Networks and to Western Power Distribution, which serves power to the Midlands, the South West region and Wales.

UK Power Networks tweeted that the outages were "due to an issue on the national transmission network," adding, "we believe all supplies have been restored."

Earlier in the day, the country's National Grid Electricity System Operator tweeted about "issues" with two power generators.

We experienced issues with two power generators causing loss of power in selected UK areas. The issue is now resolved and the system has returned to normal. Anyone continuing to experience a local issue should contact their local Distribution Network Operator for assistance — National Grid ESO (@ng_eso) August 9, 2019

Urban transportation was severely impacted by the outages, if only briefly.

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