Police and neighbors said the bodies are likely those of Marcio Ferraz do Amaral, 45, his wife, Cledione, 34, and their pre-teen daughter, whose name wasn't reported.
The family had fallen behind on their rent for three months, their landlord and friend, Gerald Mastro, said. Mastro, who lives in Chicago, had a Florida property manager check on the family, but they didn't answer the door and an odor appeared to come from the garage, the Orlando Sentinel reported Saturday.
"There was no evidence of any forced entry into the residence at all," Orange County Sheriff's Office spokesman Capt. Angelo Nieves said. "To the naked eye, there did not appear to be any trauma" to the bodies.
The sheriff's office said the deaths were likely a murder-suicide.
Mastro said the family had been having financial troubles.
Authorities were planning to run DNA tests on the bodies to confirm their identities, the Sentinel reported.