A fire that had been burning for nearly seven months in northern NSW has finally been extinguished, after a unique effort from several organisations.

The Rural Fire Service and Fire & Rescue NSW were joined by the Department of Primary Industries and Environment, Port Macquarie-Hastings Council, and the Department of Health in extinguishing the Lindfield Park Road fire, which had been burning since July 18 last year.

An RFS volunteer inside the Lindfield Park Road fire ground in January. Credit:Kate Geraghty

Of the 858 hectares, roughly 400 of them were burning underground at the wetlands south-west of Port Macquarie, fuelled by decomposed organic matter, meaning that conventional firefighting methods could not cut it.

"Typically the fires we deal with day-to-day are surface fires; leaves, sticks, trees up to the treetops. The issue with this fire, and what made it unique, is that it's old and dried up wetlands," RFS spokesman James Morris said.