“I can’t recall seeing a fire like this in a tower block in my service,” Matt Wreck, general secretary of the Fire Brigades Union, told Sky News. “It is absolutely appalling.”

Wreck said it was “absolutely remarkable” that the fire had spread as it had. “It should not be possible for a fire to develop in this way,” he said, as usually firefighters would tackle the blaze from the inside, working through the building methodically and using the internal fire escapes to move.

“There will clearly need to be a major investigation into what happened here,” he said, stressing that as the situation was still developing, more facts would emerge to allow a better understanding of the blaze.

Meanwhile, a firefighter who had been on the scene since about 1:30am described the “nasty” and “difficult” situation to BuzzFeed News.

“It was nasty in there, it was a difficult situation,” he said. “I believe the building is safe. I’ve heard that it should be stable. We’re still sending people in there and we wouldn’t do that if it was unstable.”

He added that the London Fire Brigade would be on scene for at least the next couple of days.

In a further statement, the Fire Brigades Union said all thoughts would be with those affected by the “horrific” events at the tower block as firefighters continued to work under “very difficult” circumstances.

“The thoughts of firefighters from all over the UK will be with the victims of this devastating tragedy and their families,” Wreck said. “Lives have been lost, many people have suffered serious injuries and others will be made homeless as a result of the fire.

“Firefighters and other emergency services have been working through the night to secure the building and to save as many lives as possible. They will be doing a particularly difficult job witnessing brutal scenes of such tragedy, with the professionalism we have come to expect from them.”

–Rose Troup Buchanan and Hannah Al-Othman