Police are treating a fire that destroyed possessions stored in a Wellington storage facility on Friday as suspicious.

The fire, one of the largest Wellington has seen for a long time, burned out the entire top floor of the Kiwi Self Storage unit in Kilbirnie.

It started about 12.45am on Friday and reached a ``fifth alarm'' _ the most extreme end of the Fire Service's response scale.

Today, Detective Sergeant Peter Middlemiss of Wellington police said the blaze was being treated as suspicious.


He could not confirm if the fire started inside the building.

The top floor of the building was destroyed by the blaze, while the ground floor appeared to have suffered only smoke and water damage.

The fire has prompted calls for sprinklers to be installed in large commercial buildings.