Updated

At least seven high-rise apartment buildings in England have combustible external panels similar to what was found at the London tower that went up in flames last week, killing 79 people, the government said.

British Prime Minister Theresa May's office said tests were being conducted Thursday in buildings across the country after people raised concerns about the flammable external panels which may have helped spread the flames that engulfed Grenfell Tower in West London on June 14, Sky News reported.

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Smoke billows from a tower block severly damaged by a serious fire, in north Kensington, West London, Britain June 14, 2017. REUTERS/Neil Hall - RTS16ZRN

"The relevant local authorities and local fire services have been informed, and, as I speak, they are taking all possible steps to ensure buildings are safe and to inform affected residents," May said.

About 600 buildings have cladding similar to the tower. The Department for Communities and Local Government later said that figure refers to buildings with all types of cladding and that not all of them necessarily have cladding made from the same aluminum composite material as Grenfell Tower. Landlords are being asked to check what the cladding on their buildings is made from.

An investigation into whether Grenfell Tower met fire safety regulations will also be conducted. Fire engulfed the 24-story building in less than an hour, causing officials to question how the blaze was able to spread so quickly. Authorities have not specified what started the fire.

The buildings that did contain combustile cladding were not identified. The Department for Communities and Local Government said it is giving landlords time to inform residents before the names were released.

LONDON FIRE: POLICE RELEASE IMAGES OF DEVASTATING TOWER INFERNO

May encouraged the owners of both public and private tower blocks around the country to quickly forward samples of any similar material for testing. The government will work with local authorities to make sure any dangerous material is removed and residents are safe, she said.

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Flames and smoke billow as firefighters deal with a serious fire in a tower block at Latimer Road in West London, Britain June 14, 2017. REUTERS/Toby Melville - RTS16Z80

Opposition leader Jeremy Corbyn called for urgent checks on around 4,000 buildings as Britain comes to grips with the potential ramifications of the disaster. Thousands need urgent assurances about their own safety, he said.

"At least 79 people are dead — it is both a tragedy and an outrage because every single one of those deaths could and should have been avoided," Corbyn said.

Corbyn compared the tragedy to the 1989 Hillsborough disaster in which 96 people were killed in the crush of a crowded soccer stadium, and recent sexual abuse scandals involving vulnerable children, arguing that the government had long turned a blind eye to the needs of the poor.

"The pattern is consistent: Working-class people's voices are ignored, their concerns dismissed by those in power," he said.

May has apologized for mistakes that were made in the aftermath of the Grenfell Tower tragedy and promised that "no stone will be left unturned" in a public inquiry into its causes.

"For any guilty parties there will be nowhere to hide," she said.

May's comments came after the resignation of the top administrative official in the local government that serves the community devastated by the fire. Local residents and the central government have criticized the response to the tragedy.

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Nicholas Holgate, chief executive of the Kensington and Chelsea council, had come under intense pressure following last week's blaze. The first few days after the fire were marked by chaos on the ground as local authorities struggled to deal with the hundreds of people who were displaced.

Survivors who had lost everything found it hard to find information about missing loved ones or the services available to help them get back on their feet.

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The Associated Press contributed to this report.