An Avon police officer was on patrol around 5:45 a.m. when she noticed flames rising from a medical office between West Avon and Dale roads, fire officials said.
The heavy fire started in the lower level of the two-story building that houses Avon Medical Group and Clinic Laboratory Partners, according to Tom Kline, assistant chief of the Avon Volunteer Fire Department.
Kline said that the fire was a "stubborn" one to put out and that it had a "head start" before firefighters arrived. It took about an hour and a half to extinguish the fire.
Due to the smoke damage to the building, the medical offices will remained closed for an "undetermined" amount of time, he said.
Clinical Laboratory Partners is redirecting patients to its other Avon locations in the Healthtrax building at 100 Simsbury Rd., suite 207, and the Hartford Hospital Family Health Center at 339 West Main Street, according to Spokesperson Rebecca Stewart.
The building was unoccupied at the time of the fire and Kline said that as far as he knows no firefighters were injured.
The Avon and state fire marshals are investigating the cause of the fire.
Simsbury and Canton firefighters assisted the Avon crews and Tunxis Hose Fire Department also responded. The Farmington Fire Department covered Avon's Company 1 headquarters on Darling Drive in case any calls came in for other incidents.
Avon police and American Medical Response were also on scene.