Residents of London’s Grenfell Tower high-rise were wrongly told to stay in their apartments as fire raged through the building, aided by flammable external cladding that didn’t meet safety standards, an expert report said Monday.

Fire-safety engineer Barbara Lane said the fire service’s “stay put” policy had “effectively failed” barely a half-hour after the fire started early on June 14, 2017. But, she said, residents weren’t told to evacuate for more than an hour after that.

Lane’s report was published by an inquiry investigating causes of the fire, which killed 72 people. The blaze started with a faulty refrigerator in one apartment and quickly raced up the 25-story building.

Lane’s report said that a 2016 renovation installed flammable aluminum-and polyethylene cladding on the tower’s facade and led to “multiple catastrophic fire-spread routes.”

“The assembly failed adequately to resist the spread of fire” to an extent that would have support a “stay put” policy, she said.

The judge-led inquiry, which is expected to last about 18 months, aims to find the causes of Britain’s deadliest fire in decades and to prevent future tragedies.

It will examine how the blaze spread so quickly, the response of emergency services and local authorities, and the country’s high-rise building regulations. But some survivors are critical because it won’t investigate wider issues around social housing.

“The fundamental question which lies at the heart of our work is how, in London, in 2017, a domestic fire developed so quickly and so catastrophically that an entire high-rise block was engulfed,” said Richard Millett, chief counsel to the inquiry. “And how it was that 71 people lost their lives in a matter of hours, leaving families and friends in shock, grief and bewilderment.”

A 72nd victim injured in the blaze died in January.

Millett said that survivors and bereaved relatives had been left with “an abiding sense of injustice, betrayal and marginalization, leading to an overwhelming question: Why?”

The inquiry is one of the biggest ever held in Britain, involving dozens of lawyers representing more than 500 “core participants,” including residents of the tower. It will hear from scores of witnesses, including police, firefighters, experts and survivors who escaped the fire.

Monday’s hearing follows almost two weeks of personal tributes from friends and family aiming to ensure that the victims — who ranged from an 84-year-old woman to a stillborn premature baby — aren’t forgotten during many weeks of detailed evidence on building regulations, fire-safety procedures and government policies.

Some residents accuse officials in Kensington and Chelsea, one of London’s richest boroughs, of ignoring their safety concerns because the publicly owned tower was home to a largely immigrant and working-class population.

Judge Martin Moore-Bick has assured survivors that “my team and I are determined to provide the answers that you seek.”

Grenfell United, a group representing survivors and bereaved families, said the inquiry was “the beginning of a long road to justice.”

The group, which accuses local authorities and the government of failing to heed residents’ safety warnings, said “the scale of the tragedy has devastated our lives and our community. What makes it even worse for us is the knowledge that these deaths were completely avoidable.”

Police say they are considering individual or corporate manslaughter charges in the blaze, but no one has yet been charged.

(AP)