London Fire Commissioner Dany Cotton said there had been a "number of fatalities" but could not say how many due to the size and complexity of the building.
As soon as he opened it and smoke started pouring in, he "slammed the door shut - didn't even lock it, I just slammed it shut - because I didn't want the kids to suffocate".
Muna Ali, 45, said: "The flames, I have never seen anything like it, it just reminded me of 9/11". He said that the patients were being treated for a range of injuries and smoke inhalation.
It also confirmed 20 people are now in critical care.
"They were saying apparently the fire was caused by a fridge freezer, don't know how true that it is but the way the fire spread from the fourth floor all the way up was just scary". Flames could still be seen more than 11 hours later.
The cause of the fire is not known at this stage, London Fire Brigade said.
The apartment block was built in 1974, but had recently undergone a major refurbishment, including a new heating and hot-water system, Paget-Brown said.
Six fatalities have been confirmed following the blaze at Grenfell Tower in north Kensington.
Witnesses described hearing screams, watching people jump out of the high-rise block and a baby being dropped out of a window and caught on the street below.
Witnesses have described seeing parents throw children out of the London tower block engulfed by flames as others cried for help unable to escape the "nightmare" fire. Some people were trapped in the fire, with residents desperately shouting for help from windows on upper floors as the fire spread, some British media reported.
He added: "That's when I noticed the fire from outside when I looked out the window".
The area is being evacuated and the people who have escaped from the horrific scenes can not believe they are still alive to talk about what happened. I saw a man who flew out of his window, I saw people screaming for help.
He says there was heavy smoke in the hallway and he couldn't find the stairs. She said her friend, with her five children, were all unaccounted for.
"There were people banging on windows screaming, crying out for help".
London Fire Brigade was first called at 12.54am on Wednesday morning to the Grenfell Tower in Latimer Road. It was fire up, up, up. "Only a catastrophic event will expose the ineptitude and incompetence" of the building's managers, they warned in November a year ago, adding that the event would probably be a fire, and the blog would serve as "damning evidence of the poor safety record".
The disaster occurred 10 days after a terror attack at London's Borough Market.
"All I can see is people gathered - there are bits of ash falling down from the building everywhere".
He said he saw people waving flashlights from the top levels of the building and saw rescuers "doing an incredible job" trying to get people out.
Abdul Hamid, 51, lives on the 16th floor lost everything he owned but counted himself lucky to be alive.
Other survivors spoke of confusion and conflicting advice given to residents, many of whom had been advised in advance not to leave their apartments in the event of a fire.
"I consider this mass murder, " he said of the blaze.
"This matter is of particular concern as there is only one entry and exit to Grenfell Tower during the improvement works", read a blog post by the Grenfell Action Group.
Methrob said residents had been concerned about safety, adding there had been warnings "for over a year". It recommended that in case of a fire residents should stay inside their apartments.