LONDON (AP) — Operators of Britain’s electricity network say a power cut that affected a million people and caused travel chaos was not the result of a cyberattack.

National Grid spokesman Duncan Burt says Friday’s blackout happened when two power stations failed almost simultaneously, leading the system to cut off power to 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.”

Burt said the loss of two power plants was a “very, very rare event” and something similar last happened in 2008.

The cut hit large areas of Britain, knocking out traffic lights and bringing electric-powered trains to a standstill. Electricity was restored within 90 minutes, but many travelers were stuck on trains for hours.