Spain's government said Sunday it needs more time to determine the cause of the 28 April nationwide blackout that also affected Portugal and parts of southwest France.

Environment Minister Sara Aagesen told El País that “all hypotheses” are being considered, including a cyberattack and a possible imbalance caused by solar panels in southeast Spain, as suggested by grid operator Red Eléctrica.

“We know that those installations stopped working in the system,” Aagesen said, but warned against rushing to blame renewables. “Talking about solar panels (as the cause) might be hasty” and “irresponsible and simplistic.”

The outage knocked out power, phone and internet services, halted trains, and trapped hundreds in elevators. Aagesen dismissed claims that renewables overloaded the grid, noting the system had handled similar conditions before.

“Renewable energy allows Spain to achieve a great deal of energy independence in a geopolitically vulnerable world,” she said.