UPDATED 9.17am: The cameras are out on Paeroa's main street, as onlookers take photos of the site of this morning's fatal fire.

One person died in the blaze, which fire crews were called to at about 1am.

It broke out in a jewellery store, and a body was found in a flat at the back of the building.

Specialist fire investigators have arrived at the scene.

A local says police and fire investigators have set up a cordon, and a small number of onlookers are taking pictures.

The roof of the building collapsed while crews were fighting the blaze.

Shift manager Colin Underdown says it was too dangerous for crews to search the building any earlier than they did.

"Because it was quite well-involved initially they were doing an external attack under they could get it controllable enough to conduct a search."

It's not clear how the blaze started, or if it was suspicious.

Colin Underdown says the alarm was raised just after 1am when a member of the public activated the call button at the local fire station.