The fires, including the most serious at South Oxfordshire District Council, occured early morning within a five-mile radius.
No one was injured in the fire.
At the peak of the incidents, 27 fire crews were tackling the blazes at a thatched house, the district council offices and a funeral home in two villages in South Oxfordshire.
A spokeswoman for Thames Valley Police said: "We are attending and we are investigating."
The police said a 47-year-old local man has been arrested on suspicion of arson and is currently in custody.
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"We are in the process of dealing with three major fires in South Oxfordshire, which occurred within a very short timeframe," said David Etheridge, chief fire officer for Oxfordshire Fire and Rescue Service.
"At this stage, I am unable to state what the causes of the fires were - this matter is currently in the hands of Thames Valley Police, with whom we are working in conjunction."
South Oxfordshire District Council said most of its services have been affected by the fire at its office.
"We are putting our business continuity plan into place to make sure the effect on the most important services is kept to a minimum.