Argentina blackout: Buenos Aires hit by huge power cut
Power company Edesur said about one million people in the south-central area of the city were affected.
The outage was traced back to a fire at a substation, it said.
Power cuts are not uncommon in Buenos Aires in summer, usually caused by hot weather creating surges in demand.
In June 2019, a massive electrical failure left tens of millions of people in the dark in Argentina and also in neighbouring Uruguay.
The latest incident briefly stopped trains running on at least two metro lines, reports said. Traffic lights stopped working in more than a dozen districts, causing gridlock.
The city's fire service confirmed that it had tackled a fire near an electricity substation and pictures on social media showed smoke rising from the ground next to a pylon.
By Tuesday evening supplies had been restored to nearly all customers, Edesur said.
In October, Energy Minister Darío Martínez told Clarín newspaper that Buenos Aires residents could expect "many power cuts" which he attributed to a lack of investment.