LONDON — The official cause may not be known for months. The death toll is unclear – and rising. No one has said exactly where the fire started. But experts suspect recent renovations at the Grenfell Tower, including newly installed external cladding, played a tragic role in spreading the fire so quickly.

A look at the photos and video of the inferno that claimed at least 17 lives shows why the cladding is a possible culprit: The flames can be seen “climbing” up the sides of the public housing building at an alarming pace, overwhelming efforts to limit the destruction.

The exterior cladding and the insulation squeezed between its panels were added as part of an extensive renovation completed last year. Matt Wrack, leader of the Fire Brigades Union, said that changes made during the refurbishment project seem to have left the building vulnerable to a catastrophic blaze.

“No one knows if it’s cladding or one of the other alterations,” Wrack said. “Something clearly affected the fire protection. Cladding is clearly one of the things that has to be looked at. We need to look at what happened to cause such a major failure. How can this happen in the UK in 2017? It’s staggering. It looks to me it could have been prevented.”

He said the public has a right to know the cause. Giving urgency to the quest for answers is the fact that other buildings in Britain and throughout the world use similar materials. Britain has ordered checks at tower blocks that have had comparable renovations or are being renovated now with similar methods.

On Thursday, London police said an investigation had been launched to determine whether the blaze involved any crimes, and Prime Minister Theresa May announced a public inquiry, a type of probe that’s used to investigate issues of major public concern.

Grenfell Tower’s residents were operating under “stay put” guidance in case of a fire under the assumption that modern fire doors would protect them in their apartments until the fire department could safely get them out. But the blaze spread too quickly up the sides of the building for that plan to work.

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