Police are still trying to determine how the June 14 blaze spread so quickly.
'Preliminary tests on the insultation samples collected from Grenfell Tower show that they combusted soon after the test started, ' she said.
Samples of insulation from the tower and equivalent aluminum composite tiles sent by police for analysis have failed safety tests, McCormack said.
She said: "Although we have concerns that the fire-retardant cladding used may not adhere to recognised government guidance on compliance with the building regulations for use in high-rise buildings, an independent fire expert has assured us that these hotels are safe and that they are entirely satisfied that there are robust fire safety measures and evacuation procedures in place to protect our guests and team members".
Thousands of people are now considering evacuating their homes in tower blocks across the United Kingdom after it was found that at least 14 high-rise residential buildings have a similar flammable cladding to that used on Grenfell Tower.
Hotpoint said Friday that "words can not express our sorrow at this awful tragedy" and added it was working with authorities to examine the appliance.
Officials have formally identified nine of the victims who died in the fire, and authorities are continuing to work to identify remains.
The Hotpoint fridge freezer in question. Hotpoint
The block was refurbished by the same contractor as Grenfell Tower, construction company Rydon.
The specific FF175BP model that burst was not found to be on any previous product recall list or classified as risky in any way. The material used in the cladding is banned in the United States and can not be installed higher than 40 feet, the limit of most fire fighters' ladders, in some areas of Europe. 'The initial tests on the cladding tiles also failed the safety tests'. We are not interested in people's reasons for being in Grenfell Tower'.
On Thursday, Prime Minister Theresa May said the government can test more than 100 buildings a day, and that some tests of cladding on similar large residential buildings have found them to be combustible. But, McCormack said, "Next week we will be installing a lift to the outside of the building to assist the recovery process".
As police continued to unpick the roots of the disaster, Ms McCormack said a string of criminal offences were now being considered.
"We have also listened to over 600 emergency 999 calls made to the fire brigade, ambulance service and police to understand the events of that night", McCormack said.
The death toll is expected to rise as some local residents suggest that after the fire broke out not many people could escape because the blaze engulfed the entire building rapidly.
Tánaiste Frances Fitzgerald has said she wants recently built blocks tested to avoid a London-style fire.