More than 40 firefighters fought a blaze that destroyed part of a GP surgery in Poole.
The fire at the practice in Culliford Crescent, Canford Heath, started around 2.30am in the early hours of Tuesday morning.
It destroyed the roof of the building according to a fire service spokesman.
Poole firefighters were first on the scene but quickly called for back-up.
The cause is believed to be arson after a wheelie bin was set alight by the front door of the surgery.
Dorset Police are investigating another suspicious fire in the shopping precient.
The surgery is part of the Canford Heath Group Practice which is based in Mitchell Road. It serves one of the largest estates in the UK.
Main appointments which were due to take place today at the surgery will now take place at the Mitchell Road practice.
Local ward councillor Chris Matthews who lives nearby said: "It's devastating for the community. "This a very well used surgery running a full service thoughout the week and I am horrified by what's happened." He said the council would liaise with the doctors to see if there was any help they could offer.
Dorset Police are also investigating criminal damage to three bus shelters overnight in Hasler Road where glass was shattered.