LONDON (CNN) -- London's Metropolitan Police Service said Friday it is considering manslaughter charges among the criminal offenses that may have been committed in relation to last week's deadly Grenfell Tower fire.
The police investigation is focused on how the blaze started, how it spread and whether any person or organizations should be held responsible, Detective Chief Superintendent Fiona McCormack told a press briefing. Documents have already been seized, she said.
McCormack said the number of people dead or presumed dead remains at 79, but she fears the true number could be higher. She appealed for people to come forward with information about anyone who may have been in the building on the night of the fire.
UK authorities have given assurances that they will not check anyone's immigration status as a result of information given to police in relation to the blaze. The 24-story high-rise was home to 125 families, but visitors may also have been in the building when the flames took hold.
Speculation has focused on the role that cladding apparently used in a recent refurbishment of the tower may have played in the fire, which appeared to spread quickly up the exterior of the tower in the early hours of June 14.
McCormack said samples of the cladding sent by police for analysis had failed safety tests.
The fire started in a Hotpoint fridge-freezer that was not previously part of any recall, McCormack said.
Suspect cladding found on 11 high-rises
The UK government said Thursday it was carrying out tests on 600 high-rise buildings across England that are covered in cladding, with at least 11 high-rise buildings so far identified as having combustible panels.
The affected buildings, housing potentially thousands of residents, are in eight local authority areas, including Manchester, Plymouth and Camden in north London, Communities and Local Government Secretary Sajid Javid said in a letter to lawmakers.
Addressing Parliament earlier Thursday, Prime Minister Theresa May said a statement on the test results of the cladding samples taken from Grenfell Tower would be made in the next 48 hours.
She added that the government could test more than 100 samples a day, with the results coming within hours.
Camden residents fear fire threat
Camden Council said it was preparing for the immediate removal of cladding from five tower blocks on its Chalcots Estate after tests revealed that the panels were made of aluminium with a polyethylene core -- similar to those used on Grenfell Tower, although fitted differently -- and that it had introduced extra fire safety measures in the interim.
These include round-the-clock fire patrols on estate corridors and additional fire safety checks, it said. The council said it had told the contractor that installed the panels it was taking urgent legal advice.
"I cried when I heard the news, I was in shock," resident Simon Morris told CNN. "I still am shocked, but along with the other residents I'm suffering a combination of shock and anger."
Another resident, Sayed Meah, said: "We've never had any fire evacuation rules, any plans, any procedures, nothing. So we're scared, we're genuinely scared (for) our lives."
Rosie Closier said the situation had added to her fears, saying she was "a lot more anxious because we already planned what we're going to do if there was a fire when I do have my baby. We've got it all set up in a room next to the door so we can just leave straight away, but it is really nerve racking."
Some anxious tower block residents have seen contractors abseiling from the tops of their buildings to collect samples of cladding to be sent for analysis.
