There'll be an investigation into a fire lit by an inmate at Waikato's Spring Hill prison

Staff quickly extinguished last night's blaze... but some prisoners had to move rooms for the night, because smoke spread through the ventilation system.

The unit's expected to be up-and-running later today, after checks and cleaning.

Fire and Emergency will investigate, and police will be notified.

Corrections says the man who started the fire's been moved to the Intervention and Support Unit, and charges are expected to be laid.

A spokesperson says three prison staff suffered smoke inhalation.