A spokesman for
Oxfordshire Fire and Rescue Service said the incident was being treated as arson.
Oxfordshire Fire and Rescue Service said operators took multiple calls about the blaze in Wantage, attended by three fire engines.
Paul Molloy, of
Oxfordshire Fire and Rescue Service, said they escaped safely on Friday.
Dave Etheridge,
Oxfordshire Fire and Rescue Service chief fire officer, said the families of the missing were "obviously distraught".
Oxfordshire Fire and Rescue Service said the planning department was worst hit by the blaze at the council office, which damaged around 85% of the building.
Oxfordshire Fire and Rescue Service led a massive operation to bring all three blazes under control and at its peak 27 crews were tackling the fires which started within 10 minutes of each other shortly after 3am.
Matt Carlisle, of
Oxfordshire Fire and Rescue Service, said: "When we arrived there was a well-developed fire 150m from the base involving electrical components."
With
Oxfordshire Fire and Rescue Service confirming that waters in Oxford had begun to subside, experts warned of the dangers of disease left behind.
A spokesman for
Oxfordshire Fire and Rescue Service said the plane came down on a road between Kidlington and Banbury.
Dave Etheridge,
Oxfordshire Fire and Rescue Service Chief Fire Officer, said: "We have just spoken to the families, who are obviously distraught.