Two fire investigators are looking into what sparked a large blaze in a Thames timber yard.

Eight appliances, one aerial appliance and six support vehicles battled the fire at the ITM timber supply store on Kopu Road on Sunday afternoon.

The two-storey building was in flames when fire crews arrived.

Thick, black smoke could be seen billowing from the site throughout the afternoon.

Initially people were thought to be inside the building, but everyone had been accounted for.

The blaze was under control by early evening but crews remained at the scene dampening down hot spots until past 9pm, fire and emergency northern communications shift manager Carren Larking says.

Two fire investigators had examined the scene on Sunday evening, says Carren.

There were no injuries.

Fire crews from Thames, Ngatea Puriri, Paeroa, Tapu and Hamilton helped extinguish the blaze.

-Stuff.co.nz/Ruby Nyika.