A widespread and unexplained power outage knocked out electricity in most of Spain and Portugal on Monday, shutting off traffic lights and causing chaos at airports, train stations and on the roads.

BARCELONA, Spain (AP) — A major power outage hit Spain and Portugal on Monday, including their capitals, knocking out subway networks, phone lines, traffic lights and ATM machines. It is rare to have such a widespread outage there. Spanish generator Red Eléctrica said it affected the Iberian peninsula and the incident is being assessed.

Some 96 departing flights from Portuguese airports have been grounded so far, while 45 have been called off from Spain.