Six people inside the Dix Hills home were taken to a hospital suffering smoke inhalation. Police later said they were treated and released. A firefighter also suffered a minor eye injury, officials said.
Investigators from the Suffolk County arson squad were called to the scene after Dix Hills Fire Chief Larry Feld deemed the blaze suspicious. The fire was reported at 4:59 a.m. and was extinguished about 45 minutes later, Feld said.
He referred the case to the arson squad "because of the intensity of the fire, and also being that who belongs to the house."
Police confirmed that the victims included the rapper's former girlfriend, Shaniqua Tompkins, and two of her children, including a son fathered by 50 Cent. The other three adults in the home were not immediately identified.
A passing off-duty police officer helped rescue the six people off an elevated deck in the home's backyard, Feld said.
Earlier this year, Tompkins filed suit against 50 Cent, whose real name is Curtis Jackson, claiming he had promised her the $2.4 million house more than a decade ago, but that since their breakup he now wants to evict her and their 10-year-old son from the home.
Tompkins' lawyer, Paul Catsandonis, told The Associated Press in a telephone interview that the dispute over the house had become "extremely, extremely contentious" in recent days. Although he declined to be specific, he said there was an "extremely dangerous incident" on Monday in his Manhattan office while taking a deposition for the lawsuit.
The dispute was "involving the parties in question," he said.
He said the case was back on the calendar in state Supreme Court in Manhattan on June 10.
Brett Kimmel, an attorney for 50 Cent, did not immediately return calls for comment Thursday.
Catsandonis said the 32-year-old rapper paid about $2.4 million for the house, one of the largest in the Long Island neighborhood of Dix Hills. He said 50 Cent, who was shot outside his grandmother's Queens home in 2000, had told Tompkins, 32, he wanted her and their son to live in a safe and secure place.
He also contended that the rapper signed an agreement that would give Tompkins half of all the rappers' earnings as a hip-hop superstar. "Everything that's his is hers, everything that's hers is his. He memorialized in an email that he intended to give her the house."
The rapper has been nominated for 13 Grammys, including nods for the song "In da Club" and the album "Get Rich or Die Tryin'." In 2005, he starred with Terrence Howard in a semi-autobiographical movie based on that album.
He also starred in the 2006 film "Home of the Brave" as a soldier returning home from the Iraq War.