Two adults and two teenage children were found dead in a Tampa Bay-area mansion fire that appeared to have been set intentionally Wednesday, officials in Florida said.

Investigators said they were not ruling out the possibility of a homicide or murder-suicide at the roughly 6,000-square-foot home, which is owned by former tennis star James Blake but which he had rented out and has not lived in for the last two years. 

The victims have not been positively identified as the family that had been renting the home from Blake, though officials said they had contacted their relatives to prepare them for the worst.

Blake, who announced his retirement at last year's U.S. Open, was apparently out of state during the time of the fire, according to the Hillsborough Sheriff's Office. 

Neighbors first called 911 at 5:45 a.m. to report an explosion and the possibility of a fire in the well-to-do Avila subdivision, and when firefighters arrived, they found a ferocious blaze that took hours to defeat.

Once it was safe for investigators to make it inside of the home, they discovered the four bodies in separate bedrooms -- two adults in one bedroom and the two youths in two other bedrooms, according to Hillsborough Sheriff's Office Col. Donna Lusczynski.

Two of the victims had unspecified upper-body trauma, but Lusczynski wouldn't go into further detail, saying the causes of death have yet to be determined.

That wasn't the only discovery.

"We have confirmed that there were also various fireworks -- small, commercial-type fireworks -- throughout the residence," Lusczynski told reporters in a televised news briefing.

Lusczynski added that the fire was started by an unknown accelerant and said the fireworks may have been the source of the explosion heard by the neighbors.

She said it would probably take several days to identify the victims and that an investigation into the fire was underway.

Blake retired from professional tennis last year at the age of 33 after reaching a top-five world ranking at the peak of his career.

The Associated Press reported that Blake bought the five-bedroom, five-bathroom Avila home in 2005 for $1.5 million, according to Hillsborough County property records.

According to the AP, many well-known football, baseball and tennis players have bought homes in the exclusive subdivision, which has a country club and golf course.