By ELEANOR BLACK

Bystanders at Rotorua Airport were sprayed with lead shot after a pair of 2.5kg skydiver's weights plummeted 762m, hitting the ground with such force that witness thought they were exploding bombs.

The weights, made from black fabric bags filled with lead, are used as ballast to keep a falling skydiver stable.

But during a routine jump on Sunday afternoon, skydiver Gregg Eagles left his weights tucked into the pouch that held his parachute secure in its backpack.

When he released the ripcord, they fell to the ground, landing near the airport entrance with such force that police were called to investigate reports of homemade explosives being detonated.

Police thought they might have been dealing with explosives left by a bomber and detonated when a car drove over them.

They began an investigation to see if similar incidents had happened at other airports.

Reports of the "bombs" were sent out on the news wires.

One woman was slightly injured when she was peppered with lead pellets, but Detective Sergeant Mark Loper said someone could have been killed if the bags had scored a direct hit.

Mr Eagles, a veteran of more than 500 jumps, had no idea he had lost the weights until he got a phone call yesterday morning.

He said he did not see the weights because they "blended in" and he usually used larger ones made from 4-litre oil cans.

"I really don't know how it happened ... I won't be using those weights again.

"When I found out I thought, 'Oh no, what have I killed?' Somebody could have been really badly hurt," said Mr Eagles.

Dr Chris Tindle, a physicist at Auckland University, said it was difficult to know the speed and force the weights would have reached when they hit the ground. But they were probably falling at terminal velocity.

They would have had enough force to easily cave in a car roof and anyone hit would certainly have been killed.

"It would put a great big dent in almost anything it hit."

The Civil Aviation Authority is investigating.