By Laura Almanza Vollert, Rachel Boßmeyer, Marek Majewsky, Philipp Znidar, Emilio Rappold, Michael Kieffer, Juliane Rodust, Jan-Uwe Ronneburger, Marc Kalpidis, Andrea Sosa Cabrios

Madrid/Lisbon (dpa) - After the widespread blackout on Monday, almost everyone in Spain and Portugal now has electricity again.

The Spanish utility Red Eléctrica announced early Tuesday morning that over 99 percent of the power supply had been restored on the mainland affected by the outage.

In Portugal, more than 6.2 million out of a total of 6.5 million households had power again, as the responsible authorities in Lisbon announced during the night.

It is still unclear what specific causes led to the power outage on Monday at around 12.30 a.m. CEST, which the government in Madrid described as "historic" and "unprecedented".

Millions of people on the Iberian Peninsula were cut off from the outside world for hours. There was no electricity, internet or working telephone connections almost everywhere.

Eduardo Prieto, Director of Grid Operations at Red Eléctrica, told the media that the disconnection of the European electricity connection in France was responsible for the collapse on the Iberian Peninsula. However, it remained unclear what led to this disconnection.

In both Spain and Portugal, metro and train services, among others, resumed on Tuesday. Despite the slow normalization, the governments of both countries announced crisis meetings to evaluate the situation.

On Monday, countless people in Portugal and Spain were stuck in trains, subways and elevators during the day. Vacationers were stranded at airports, and the internet and telephone networks were also down. Traffic lights failed, hospitals had to switch to emergency operation with power generators and many Spaniards and Portuguese on the mainland were effectively unable to work.

In Madrid, the international Masters 1000 tennis tournament with top players such as German professional Alexander Zverev (28) also had to be interrupted. Play is due to resume on Tuesday.

When the lights suddenly came back on long after dark, Madrid residents cheered loudly in the streets, from windows and balconies. Cries of joy such as "Siii" (Jaaa) and "Vivaaa!" (Hurraaaaa) could be heard from moving cars, while other people enthusiastically sang the famous song "Y Viva España".

However, according to the Federal Network Agency, there is little reason to fear such a large-scale power outage in Germany.

"A large-scale, long-lasting blackout is unlikely in Germany," said the agency in Bonn at the request of Deutsche Presse-Agentur.

The German power grid is designed to be redundant.

This means that the failure of one line would be absorbed by another line.

First reported at 6.42 a.m., last updated at 7.47 a.m.