A minor electrical fire has forced the temporary closure of the National Archives Preservation Facility at Mitchell in Canberra.

The fire in a dehumidifier unit started around 4.00am Monday morning and was quickly extinguished by responding ACT Fire and Rescue crews.

Preliminary investigations show no damage to records stored in the facility's repositories.

National Archives of Australia Director-General David Fricker said, 'The National Archives Preservation Facility houses a significant component of the national archival collection, which is valued at nearly $1.5 billion. Among the precious collection items held at the Mitchell repository are the iconic Griffin designs for Canberra.

'This incident serves to remind us how devastated our nation would be if these items were forever lost. Protecting and securing the records that represent the nation’s memory are, and will remain, a key priority for the National Archives.'

National Archives staff and representatives of the building owners responded to the fire and remain on site to assess the impact and monitor air quality.

Full mechanical services to the building have resumed.

A full investigation into the cause of the fire will be undertaken.

It is expected the building will reopen by tomorrow.