Naval Station Rota was affected by a major power outage that hit Spain and Portugal.

The widespread power outage was being felt at U.S. Naval Station Rota in Spain’s Andalusia region, but the base’s operational abilities, including flight and ship operations, remain unaffected, said Lt. Danny Ehrlich, a spokesman for the base. NS Rota, which includes an airfield, is home to five Navy destroyers, among other operations.

Rota public works personnel were working to restore power to the base using an on-base generator, said Ehrlich, who did not specify if residences and other facilities, such as the commissary, Navy exchange or schools, had electrical power.

“We’re ensuring our sailors are taken care of,” he said.

The 496th Air Base Squadron also operates in Spain at Moron Air Base, about 75 miles northeast of Rota. It was not immediately clear if the power outage had impacted the squadron’s operations. The squadron is part of the 65th Air Base Group in Lajes, Portugal, which operates under the 86th Airlift Wing in Ramstein, Germany, according to the Air Force.

At some places in Spain and Portugal, subway networks, phone lines, traffic lights and ATM machines were knocked out, according to The Associated Press. The countries have a combined population of over 50 million people. It was not immediately clear how many were affected.

Spanish power distributor Red Eléctrica said that restoring power fully to the country and neighboring Portugal could take 6-10 hours. By mid-afternoon, voltage was progressively being restored in the north, south and west of the peninsula, the company said.

It is rare to have such a widespread outage across the Iberian Peninsula.

The blackout is the second serious European power outage in less than six weeks after a March 20 fire shut down Heathrow Airport in the U.K. and comes as authorities across Europe gird against sabotage backed by Russia.

While the causes of the Iberian blackout were still being investigated, Teresa Ribera, European Commission executive vice president in charge of promoting clean energy, told Spanish journalists in Brussels there were no indications of a cyber attack in Monday’s power outage.

Spain’s public broadcaster RTVE said a major power outage hit several regions of the country just after midday local time, leaving its newsroom, Spain’s parliament in Madrid and subway stations across the country in the dark.

A graph on Spain’s electricity network website showing demand across the country indicated a steep drop around 12:15 p.m. from 27,500MW to near 15,000MW.

Video aired on Spanish television showed people evacuating metro stations in Madrid and empty stations with trains stopped in Barcelona.

Spain’s traffic department is asking citizens to avoid using their cars as much as possible due to the power outage, which has affected traffic lights and electrical road signage.