Fire trucks and diggers are being used to fully extinguish the remains of a massive fire at a recycling centre in Auckland

Crews have been working around the clock to put out the last remaining hotspots at the Wairau Valley plant.

Assistant Commander James Hall says while there are small flare ups, the lithium-ion batteries involved in the fire are no longer a hazard.

An investigation into the cause of the fire is underway.

Crews are expected on site until this afternoon.