Investigators are looking into a suspicious fire in Whanganui that's left two people with serious injuries

The fire happened at a three storey heritage building on the corner of Victoria Ave and Taupo Quay in the city centre last night.

Two people have been taken to hospital to be treated for burns and smoke inhalation.

More than a dozen fire crews from as far away as Palmerston North were called in to help deal with the fire.

Investigators are due back at the scene this morning.