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 to both countries.

Alanna Gladstone, a 40-year-old film editor, had landed in Portugal’s capital, Lisbon, on a flight from New York hours before the outage. She checked into her Airbnb and took a nap; by the time she woke up, the technology that the country takes for granted had gone dark.

Electricity was back in most of the two countries almost 18 hours after a blackout that shut down much of daily life. The cause of the outage remained unclear.