Video: Residents in Auckland's Epsom able to return home after Defence Force detonates backyard mortar

Residents on streets in Auckland's Epsom have been told they can return to their homes after being evacuated because of an old bomb found in the area.

A thudding bang rang out into Pukenui Rd, Epsom, as police detonated the old mortar.

"The New Zealand Defence Force Explosive Ordnance Disposal (EOD) unit conducted a series of small controlled detonations and have now safely disposed of the item," a police spokesperson said in a statement.

Police added the surrounding roads have reopened and all cordons have been lifted.

"We have had to clear about 60 addresses in order to make [it] safe but that was just being extremely conservative," Shift inspector Kerry Watson said during a press conference.

On Thursday afternoon Watson added police were called to a place on Pukenui Rd after finding an old bomb.

"One of the neighbours here was doing a bit of gardening and found what he thought was an explosive device."

Watson said the EOD examined the device on Thursday evening and returned on Friday to follow their standard operating procedures and dispose of the device safely.

"What that involved was sandbagging the area, making it safe, planting an explosive device to see if it can trigger an explosion and make this safe. Once they have done that they have then ascertained that is, in fact, inert," shift inspector Watson said.

He added the defence team has been unable to confirm when and where the device was made but, "their initial assessment is that it's somewhere from overseas," shift insp Watson said.

Shift insp Watson said the defence team wouldn't have been able to establish the old bomb wasn't a danger to the residents in the area until after they had followed the standard operating procedure.