Spain's grid operator denied on Wednesday dependence on solar power was to blame for the country's worst blackout, while Prime Minister Pedro Sanchez came under increasing pressure to explain what went wrong.

Monday’s devastating blackout in Spain is raising questions about the country’s massive reliance on solar and wind power for electricity — and whether the new power sources may have played a role. Spain’s socialist government has faced increasing pressure to explain what went wrong on Monday,

Some media outlets have speculated that Spain’s April 28 blackout may have been caused by a disconnected solar plant, but DNV grid analyst Andrea Mansoldo tells pv magazine that it was likely due to a combination of grid weakness and low-frequency oscillations.