The 24-story building that went up in flames in London Wednesday recently underwent an $11 million upgrade, something that investigators will probe as they seek to understand what sparked the deadly fire, NBC News reported.
At least 17 people are confirmed dead, but many more are missing, and the death toll is expected to rise. Experts said an energy-efficient outer layer called cladding, added for aesthetics and to keep out moisture, would be a focus of the investigation.
"If the fire manages to break out and get into the cladding it melts the external metal, which is often no thicker than tinfoil, gets hold of the insulation material in the middle, and that ignites and starts to burn," litigation lawyer and construction expert Matthew Needham-Laing told the BBC.
The construction firm that refurbished the government-owned tower last year, adding "rainscreen" cladding, said the project "met all required building regulations."