A spokesman did not provide further details but said there was currently no suggestion that the power failures were linked to each other or the massive system failures that occurred on Monday throughout Spain, Portugal and parts of southern France.

Such investigations are standard practice whenever there is an unexplained power cut on the grid.

But it comes as grid stability is being closely scrutinised across Europe, with Spain and Portugal currently in the process of painstakingly re-activating their grids following the unprecedented loss of power nationwide.

Pedro Sánchez, the prime minister of Spain, refused to speculate on the suspected cause in a press conference late on Monday.

An earlier suggestion by Portuguese officials that the blackouts may have been triggered by a freak weather event have since been downplayed, leaving the events that led to Europe’s worst electricity failure in decades shrouded in mystery.

Meanwhile, Jordi Sevilla, the former president of Spain’s national grid operator, Red Eléctrica, suggested on Tuesday that the loss of power was indirectly caused by Spain’s heavy reliance on solar and wind farms.