A massive clean up and recovery phase has swung into action in the heart of Auckland's business precinct, as fire crews continue to dampen down hotspots after the SkyCity fire

This morning, exhausted firefighters remain at the site, pulling bits of iron and roofing materials out and spraying hotspots.

A large crane will be placed on Nelson St this morning to aid Fire and Emergency New Zealand, which has now launched a formal investigation into the cause and spread of the fire.

Auckland Restoration and Cleaning owner Michael Breen says much of the work required at the NZICC, would be decontamination.

There's also smoke, fire and flooding damage in the surrounding businesses.