The four men and two women, ranging in age from 18 to mid-30s, did not appear to be related, and had not been living at the house long, officials said.
Officials said they did not believe the deaths were a murder-suicide or accidental.
"It appears that we have a murderer on the loose, but it's early in the investigation," Volusia County Sheriff's spokesman Gary Davidson said.
Sheriff Ben Johnson did not offer a possible motive for the apparent slayings or specify how the victims died.
The bodies were discovered after one victim's co-worker called a friend and asked the person to visit the home after the victim didn't come to work, officials said.
Davidson said the six bodies, along the body of a dog, were found in different rooms of the three-bedroom home in Deltona, about 25 miles north of Orlando. Nobody was found alive inside.
Deputies have sealed off the area, officials said.
Authorities declined to comment on reports that some victims worked at a nearby Burger King. A restaurant sign read "Sorry temporarily closed. Sorry for the inconvenience." Don Ramdeen, the restaurant's operations director, said the business was bringing in professional counselors for its workers.
A neighbor, India Harris, 17, said investigators had quizzed her, but she knew the home's residents only well enough to say hello. County tax records show the home is owned by a man who lives in New York City's borough of Brooklyn.
By Mike Branom