"I'd say there is a strong -- a strong, strong -- possibility that it is suspicious," Dix Hills Fire Department Chief Larry Feld told Newsday.
Asked why he considered the fire suspicious, Feld said, "The rapid movement of the fire. The volume of the fire. ... It was engulfed. The home was totally gutted."
An eyewitness who works for Newsday told the newspaper 50 Cent's ex-girlfriend, Shaniqua Tompkins, and their 10-year-old son, Marquise, were among the injured.
"She was all right," Frank Hoyte said. "But she was angry."
Fire officials said the victims in the house who were taken to the hospital suffered smoke inhalation.
The house has been at the center of a legal battle between Tompkins and the rapper whose real name is Curtis Jackson.
Jackson attempted to have Tompkins evicted unless she paid rent and Tompkins filed a lawsuit against Jackson claiming breach of contract, Newsday said.
Jackson's lawyer Brett Kimmel released a statement to TMZ.com after Tompkins suggested the rapper may have been involved in the blaze.
"Any suggestion that Mr. Jackson had anything whatsoever to do with the fire at his home is outrageous and offensive," the statement said.