Senior Constable Graham Perkins said two more tubes of PowerGel, a commercial product used in construction, were found at the Clutha River bank at Miners Lane on Sunday morning.
It was about a month since the same quantity of explosives was found in almost exactly the same place, he said.
The New Zealand Defence Force (NZDF) explosive ordnance disposal team was called back to neutralise the explosive with the loud explosion about 5.30pm startling residents who took to social media to find out what had happened.
A smaller cordon was established this time and people who had parked boats in the area in preparation for jet sprints moved them upriver, Snr Const Perkins said.
There was no cost to the local community for the bomb squad’s time and on-duty police manned the cordon until they arrived.
Since last month’s find, police discovered PowerGel has been turning up from time to time since construction of the Clyde Dam.
It was believed the surplus material had been either thrown in the river or buried and when the river was low it surfaced. A senior staff member recalled people bringing tubes into the station, but they did not want that to happen again, he said.
If anyone found PowerGel they should call emergency services immediately and not touch it, Snr Const Perkins said.
