MADRID (AP) — The cause of Spain and Portugal’s widespread blackouts remained a mystery on Tuesday, with some isolated disruption remaining after power was largely restored. One of Europe’s most severe blackouts grounded flights, paralyzed train systems, disrupted mobile communications and shut down ATMs across the Iberian Peninsula on Monday.

Life in Spain and Portugal began to return to normal Tuesday, a day after a massive power outage paralyzed the Iberian Peninsula, leaving governments, companies and experts scrambling to figure out what went wrong.

Electricity has returned to most of Spain and Portugal but with continued disruptions on the second day after an unknown failure caused a massive blackout across much of western Europe.

Play at the Madrid Open tennis tournament has been suspended because of a major power outage reported in Spain and Portugal.

A major power outage reported in Spain and Portugal has shut down matches, including the one between Britain's Jacob Fearnley and Grigor Dimitrov, at the Madrid Open. Two singles matches and one doubles match were underway when the power went out.

Play was suspended at the Madrid Open the afternoon of April 28 before being canceled for the day and night, due to a power outage across Spain and the Iberian Peninsula. The loss of power meant that the electronic line calling (ELC) system used to judge whether a shot has landed in or out did not work,