Some passengers on the hot-air balloon may have been electrocuted or killed by the intense heat of a fire generated by contact with a 33,000-volt powerline before they had hit the ground, an expert says.

Eleven people died after the balloon hit or became trapped in powerlines, causing a spark or arcing in the basket which then caught fire. Two passengers jumped or fell from the balloon before it rose quickly then plunged to the ground.

The circumstances of the tragedy are being investigated.

But a power engineer told the Herald that a power line carrying such intense energy could generate heat greater than 2000C.

Advertisement

"The intense heat upon contact with the powerline and the reduced weight in the balloon because of the two people jumping off would have turned the balloon into a rocket," said the engineer.

"It is possible that most of those in the basket would have been electrocuted and may have died upon contact with the ruptured powerline."

The lines supplied electricity to 3800 homes, which were without power for several hours.

One of the questions likely to be examined is whether the outcome would have been different had two of the passengers not leaped from the balloon in mid-air.

Balloon experts say one of the key safety messages hot-air ballooning passengers are given is to never leave the basket unless the pilot says so - because the consequences of doing so can be dangerous for everyone on board.

Balloon Aviation Association president Martyn Stacey said all balloon rides started with safety checks on equipment and a passenger safety briefing which included a warning about always remaining inside the basket.

"It is critical to stay in the basket because you imagine losing 100kg and you have got a thing that weighs nothing - all of a sudden it will go racing up in the sky. If you imagine losing two passengers, which happened on Saturday, the pilot's got no control - he's lost 120kg and away he goes."

The balloon's rapid ascent could have fuelled the flames and made it more difficult for the pilot to get to the ground quickly.

The Herald understands the pilot made no emergency call to air traffic control, possibly because of the suddenness of the accident.

Heavy rain battering the region yesterday hampered efforts to remove bodies remaining at the crash site.

But the Transport Accident Investigation Commission and police have promised to "leave no stone unturned" as they work to determine what caused the fatal crash.

Wairarapa police area commander Inspector Brent Register said the bodies of the couple who jumped from the basket were removed on Saturday.

Two more bodies were removed yesterday afternoon, and police hoped to remove the remaining bodies last night and today.

- additional reporting by APN