An Auckland businessman who discovered what he is certain was a bomb in a cooler bag left in a popular Mission Bay reserve at the weekend fears it could have been very serious if the bag had been ignored.

A police spokesperson said they were still investigating the discovery of a suspicious item left at the reserve near Patterson Ave and wanting to speak with anyone in the area in the early hours of Saturday morning to confirm its exact contents and how it was left there.

Mission Bay resident Rob Hallie was walking his dog at 6.50am on Saturday when a distressed council worker ran up to him and asked for his help. He followed the rubbish collector over to a tree about 2m from the community police station where there was a light blue cooler bag containing a home-made device.

"It was unbelievable. I couldn't believe what I was actually seeing," Mr Hallie said. "This was a bomb in a reserve, which is crowded with hundreds and hundreds of people. It was a disbelief that what I was actually seeing was actually a bomb. It took a couple of seconds to sink in."


Zipped inside the soft cooler bag was a five litre plastic container full of fluid and a black wire connected two devices taped to the side and top of the container.

"It was square and obviously had some sort of mechanism in it and had a small wheel on the top which looked like a little gear. I guess that was the mechanism which was going to set off the device."

Mr Hallie called 111 and told a group of cyclists and swimmers to clear the area while he waited for police to arrive. He left the scene at 7.20am to go to work, but was contacted by the detective sergeant and the bomb squad later in the day trying to find out more about the device and who planted it. The police bomb squad detonated the chilly bin about 9.45am.

Mr Hallie wanted people to learn from this incident.

"There's this level of crime that's just surfaced that hasn't happened before. And people need to now be aware that anything like that, if it's left behind could be a device. If people had thought someone had just left it behind this could have gone off and there would have been hundreds of people there... this could have been absolutely disastrous."