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.

A massive power cut hit large parts of Spain and Portugal on Monday, causing widespread chaos and disruption. The outage left millions of people without electricity, while internet and phone networks were also down. Trains were cancelled and evacuated in some regions, traffic lights stopped working amid mounting delays at airports.

Electricity is pulsing through Spain and Portugal again after a massive outage knocked out power in both countries on Monday. So too are questions.

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,