Dramatic pictures reveal damage caused by mid-air explosion on Qantas jet - and how passengers were lucky to survive

Officials said the Melbourne-bound 747 jet, which made a forced landing in Manila on a flight from Heathrow, could be repaired for less than £5 million, despite extensive damage in the fuselage.

The news came as photos suggested only luck had prevented a chain reaction of exploding oxygen cylinders destroying the entire plane.

One exploding cylinder was officially blamed yesterday for the devastating blast, but what was not previously known was just how close the bottle was to six other green tanks, lined up along the right side of the cargo hold.

The gaping hole is just a matter of centimetres from explosive oxygen cylinders

A preliminary report issued by inspectors from the Australian Transport Safety Bureau yesterday found the faulty cylinder, fourth in the row of strapped-in bottles, 'sustained a failure that allowed a sudden and complete release of the pressurised contents'.

And photographs of the positioning of the other containers revealed the risk of an explosive chain reaction that, given the damage caused by just one tank, could have sent the aircraft plummeting.

The aircraft, with 365 people on board on July 25, immediately lost cabin pressure when the explosion tore a 5ft high and 6.5ft wide hole in the fuselage.

The rest of the cargo hold remained remarkably unscathed after the blast

The ruptured bottle was blasted up through the passenger cabin floor but everyone on board escaped injury.

'It happened very quickly,' said Mr Julian Walsh, director of the safety bureau when he released the preliminary report in Canberra.

'The oxygen bottle went from the base of the aircraft to the ceiling of the first floor cabin.'

On the way, he said, it hit the handle of the cabin door, tore a hole in the fuselage and disabled the instrument landing system and the anti-skid brake system.

Australian pilot Captain John Francis Bartels looks at the damage to a Qantas Airways plane after it made an emergency landing at the Manila International airport in July

While it did not discuss the risk of a possible chain reaction among the other cylinders, the initial report also gave no explanation why the exploding bottle failed under pressure.

It was part of a batch of 94 that had been made in February 1996 and had undergone regular three-yearly checks and investigators will now be tracking down other cylinders made from the same batch by the US manufacturer.

So far, said Mr Walsh, no other problems had been identified.

Qantas said  the aircraft would be safe to fly again once the damage had been repaired and could resume service as early as November.