Explained | What we know so far about the Spanish apartment block fire

Madrid: A fire that swept through an apartment complex in the Spanish city of Valencia, killing at least 10 people, has prompted comparisons with London's 2017 Grenfell Tower inferno and raised concerns about fire safety standards and cladding materials. Here is what we know so far about the fire, which broke out on Thursday evening, and the damage it has caused.

How did the fire start?

Authorities are investigating what caused the fire and where exactly in the building it broke out, but according to a sequence of videos posted on X by user @estella_carlos, the left corner balcony on the ninth floor of the taller of two towers was in flames at 5:37 pm (1637 GMT) on Thursday.

The blaze spread to the balcony right below within two minutes, and another 11 minutes later almost all the left side of the building and the top of the central part were ablaze.

At 6:22 pm, the fire had spread to the adjoining smaller tower.

Why did the fire spread so quickly?

Experts say that based on the available videos, a combination of strong winds, canvas balcony canopies and the facade's composite cladding materials most likely helped to stoke the fire.

Ivan Cabrera, director of Valencia University's School of Architecture, told TVE broadcaster that just as the Grenfell Tower blaze prompted changes in British fire safety legislation and led to mass cladding renovation in many properties, the same should happen in Spain.

The fire in west London started after an electrical fault, but its high death toll of 71 people was to a large extent blamed on the use of highly flammable external cladding.

How many people have died?

Spanish authorities said 10 people were confirmed dead after the first visual inspection inside the apartment complex in Valencia. A local court has opened an investigation.

According to Valencia's mayor, everyone has now been accounted for.

A total of 105 people who have lost their homes have been moved to nearby hotels. More than a dozen people, including firefighters, were injured in the blaze.

What we know about the apartment complex

The complex is in a new residential area of Valencia that was developed in the past two decades.

The stricken complex consisted of two buildings of 14 and 10 floors, linked by a panoramic lift and with an open swimming pool in the courtyard. It comprised a total of 138 apartments. The bottom two floors were commercial premises, and top-floor apartments had large terraces.

The developer, FBEX, erected the building in 2008 just as Spain's real estate boom of the 2000s was about to turn to bust. FBEX went bankrupt in 2010 and creditor banks sold most of the flats, according to El Pais newspaper. Attempts to contact its former owners have yielded no results.

Questions about materials

Valencia's city council did not reply to a Reuters' request for comment on the materials used in the building, while the city's Council of Architects said it only kept technical records of buildings for 10 years.

Esther Punchades of insurance inspection agency APCAS, who has previously assessed the building, told state broadcaster TVE a lack of firewalls and the use of polyurethane underneath a layer of aluminium cladding had allowed the fire to spread.

The plastic material, she said, tends to melt and catch fire when in contact with open flames, falling on lower floors in large fiery drops while also propagating flames upwards.

However, Spain's Association of Rigid Polyurethane Industry said in a statement there was no evidence that the composite cladding contained polyurethane, while some experts suggested the insulation material under the aluminium was rock wool.