At least three people have died in Spain in an incident linked to a massive power cut that shut the country down on Monday, the Civil Guard has told the BBC.

They died in the north-west municipality of Taboadela and were from the same family, according to Spanish media.

Police are reportedly investigating whether carbon monoxide from a faulty electricity generator played a role in their deaths, but the Civil Guard could not provide more details.

Officials are still working to confirm what caused the power cut that triggered chaos across Spain and Portugal on Monday.

The trio who died in Taboadela were a married couple and their adult son, according to the Madrid-based newspaper El Pais.

Their bodies were discovered in their beds by a care worker on Tuesday, El Pais reported.

Other deaths are under investigation, including a woman in Madrid who died in a fire that may have been caused by a candle being used during the blackout, local media reported.

The woman, in her fifties, was found dead on Monday night after a fire broke out in a building in the city’s Carabanchel district.

Thirteen people were treated for smoke inhalation, including five who were taken to hospital, according to the city’s emergency information office.

Elsewhere, a woman in her forties is reported to have died in Valencia, though there is no clear consensus in Spanish media on the cause of her death.

Local police have suggested the woman, who suffered from a lung condition, died after the ventilator she was using lost power during the outage, according to media reports.

However, El Pais cited regional health sources who said the woman suffered from a number of health conditions and that she died of natural causes.

The blackout caused huge disruption across Spain and Portugal. Andorra and parts of France were also affected.

In Spain and Portugal, traffic lights stopped working, metro systems ground to a halt, and businesses were unable to accept card payments – triggering huge queues at the few cash machines that were still working.

Initially, mobile phone networks also went down, leaving many scrambling for information.