Donald Trump's 9/11 bomb theory on the day of terror attack which destroyed World Trade Center

Donald Trump believed the Twin Towers were destroyed with bombs as well as planes on 9/11 , in an interview on the day of the terror attack.

In a phone interview with a local New York news station just hours after the World Trade Center buildings collapsed in 2001, the real estate mogul said that he didn't see how a plane could break through the steel on the buildings' sides.

The interview - 15 years before he ran for President - appeared on rolling news coverage for WWOR/UPN 9, as he gave his expert opinion as a property developer.

And he suggested that the towers were destroyed by "bombs that exploded almost simultaneously" when the planes collided with the towers.

He said: "It wasn’t architectural defect. The World Trade Center was always known as a very very strong building. Don't forget that took a big bomb in the basement [in a 1993 attack]"

He continued: "When I first looked at it I couldn't believe it because there was a hole in the steel. Remember that the width of the windows in the World Trade Center, if you were ever up there, they were quite narrow, and in between was this heavy steel.

"I said how could a plane - even a plane, even a 767 or 747 or whatever it might have been - how could it possibly go through that steel?

"I happen to think that they had not only a plane, but they had bombs that exploded almost simultaneously.

"Because I can’t imagine anything being able to go through that wall.

"Most buildings are built with the steel on the inside around the elevator shaft, this one was built from the outside, which is the strongest structure you can have. And it was almost like a can of soup"

He added: "I just think it was a plane with more than just fuel. I think obviously they were very big planes and they were moving very rapidly... it just seemed to me that to do that kind of destruction is even more than a big plane, because you're talking about taking out steel."

Trump's claims are similar to a conspiracy theory, which suggests that it wasn't planes at all that destroyed the WTC, but that the buildings were instead deliberately destroyed by explosives.

His theories have since been debunked by the official investigation into the 9/11 attacks.

The National Institute of Standards and Technology issued its final report on the Twin Towers in 2005, and concluded that it was the planes that brought down the towers.

In an FAQ published in 2006, the investigators said that "the massive damage was caused by the large mass of the aircraft, their high speed and momentum, which severed the relatively light steel of the exterior columns".

Fire proofing insulation was also damaged by the impact, and the massive amounts of burning jet fuel weakened the supporting steel, which caused the structure on the impact floors to fail, causing the collapse of the building when it couldn't support its own weight.

Trump also bizarrely used the tragedy to brag about the size of his own Trump Building in downtown Manhattan.

He said: “40 Wall Street actually was the second-tallest building in downtown Manhattan, and it was actually, before the World Trade Center, was the tallest — and then, when they built the World Trade Center, it became known as the second tallest. And now it’s the tallest.”

Presenter Brenda Blackmon has since told the Washington Post that the response left her 'stunned'. She said: “Any reaction I had, in the midst of everything that was happening, was, wow, that’s insensitive. It just was.”

Trump's bomb theory isn't the only conspiracy he has bought into concerning 9/11.

During his presidential campaign he claimed that he saw "thousands" of Muslims in New Jersey celebrating shortly after the attacks but offered no proof or corroborating witnesses.

Fact-checking website Politifact called that statement "pants on fire" inaccurate.