London police said Friday that a deadly fire last week that killed at least 79 people began in a refrigerator freezer - the first official confirmation of the cause of the blaze.

The fridge freezer, a Hotpoint FF175BP, was not subject to a product recall, police said, adding that a key concern in their investigation is how a fire that originated in the kitchen of one apartment spread so rapidly though a 24-story high-rise. The fire was not started deliberately, they said.

The police also said they are considering manslaughter charges after the insulation and tiles used in the building's exterior cladding failed fire-safety tests.

"Preliminary tests on the insulation samples collected from Grenfell Tower showed that they combusted soon after the test started," Detective Superintendent Fiona McCormack told reporters. She added that the cladding tiles also failed safety tests.

Hotpoint issued a "product notice" on Friday for the appliance identified as the source of the June 14 blaze. "We have been made aware of a possible incident involving a Hotpoint branded Fridge Freezer, manufactured between March 2006 and July 2009, model numbers FF175BP (white) and FF175BG (graphite)," the notice said.

There has been widespread attention on the building's exterior cladding. Combustible cladding has been blamed for fast-moving fires at high-rise buildings in places including Dubai and Melbourne, Australia.

Investigators said they are looking into various aspects of the facade of Grenfell Tower, including the aluminum tiles, the insulation behind them and how the tiles were affixed.

The British government is also conducting tests at hundreds of high-rise apartments to see if they have potentially flammable exterior tiles. So far, 14 buildings have been found with cladding similar to that used at Grenfell Tower.

McCormack said that manslaughter charges are among those police are considering in relation to the fire.

"We are looking at every criminal offense, from manslaughter onwards. We are looking at every health and safety and fire safety offenses, and we are reviewing every company at the moment involved in the building and refurbishment of Grenfell Tower," she said.

McCormack said that every intact body has been removed from the building and that nine of the dead have been formally identified. She added that the fire was so intense officials may never be able to identify everyone who died.

Officials have said they don't know who, exactly, was in the tower on the night of the blaze. They have stressed they will not check the immigration status of anyone who was involved in the fire or who has information about victims, in view of concerns that some people may have been staying in the building illegally.

Police have reviewed more than 600 calls made to Britain's universal emergency number on the night of the fire to try to piece together events. "Some of these calls are over an hour long and truly harrowing," McCormack said.

Many local residents say they doubt the official death toll. On the streets around Grenfell Tower, now a blackened hulk, missing-person photos are attached to railings, buildings and bus stops. One girl, Amaya Ahmedin, who turned 3 in February, is pictured in a gold party hat next to her smiling parents.

On one of the many walls of condolences, one person wrote that community sources and "info from police and ambulance" indicate there are 160 dead.

Police say that 79 people are dead or presumed dead but have suggested that the number could rise.

"I fear that there are more. I do not know who they are at the moment," McCormack said as she appealed for those with information to come forward.