The power outage experienced in the United Kingdom by thousands of homes on Friday was not caused by a cyberattack, the electricity transmission network of Great Britain said on Saturday.

Duncan Burt, operations director at National Grid, said the power outage occurred when two power stations failed almost at the same, leading the system to cut off power in some parts of the country in order to preserve the rest.

He said the company was “very confident that there was no malicious intent or cyberattack involved” but added that the loss of two power plants was a "very, very rare event" and that the last time something similar happened was in 2008.

"Even though these events are outside of our control, we have plans in place to respond and the system operated as planned by disconnecting an isolated portion of electricity demand," a National Grid spokesperson said on Friday.

Tim Green from the Energy Futures Laboratory at Imperial College London said the failures happened at a gas-fired power plant in southern England and a wind farm in the North Sea. He added it was unclear whether the events were connected or if it was just a coincidence.

A spokesperson for the UK power networks said that about 300,000 properties were affected in London and Southeast England.

A spokesperson for Western Power Distribution (which serves Wales, Southwest and the Midlands) said roughly 500,000 customers were affected "from around 4.53 pm with all customers restored by around 5.22 pm."

Britain’s energy watchdog Ofgen said it has asked for “an urgent detailed report from National Grid so we can understand what went wrong and decide what further steps need to be taken. This could include enforcement action.”

Photos and videos showed chaos in train stations and London's Tube stations. Travellers experienced heavy delays and some train stations closed. National Rail told travellers to expect hour-long delays and cancellations.