Firefighters are using thermal imaging equipment to make sure a fire at an Auckland scrap metal recycling site is out after reports of an explosion.

They have been called to National Steel on Hobill Ave in Wiri and are cooling down a compacting machine that caught fire.

Fire crews rushed to Wiri after a 111 call reported an explosion, but staff have not been able to say if there was one.

A fire investigator is at the scene.

The Fire Service said it had no reports of anyone being hurt.