Daniel Smith, 20, died in his mother's hospital room Sept. 10, 2006, three days after she gave birth to daughter Dannielynn.
Smith died Feb. 8 in a Hollywood, Fla., hospital where she was taken after being found unresponsive in a nearby hotel room. A cause of death hasn't been determined.
Bahamas chief magistrate Roger Gomez told CNN that authorities now have a greater interest in questioning Stern. The official said Smith and Stern were in the hospital room when Daniel Smith died.
"Anna Nicole, the mother of Daniel, is dead, and Howard is the only one who was alive who was in the room," Gomez said. "And it really arouses our suspicions to exactly what happened in the room."
Ron Rale, a lawyer for Smith's estate, said he gave "no credence" to any suspicions of wrongdoing.
"It's going to unfold, and everyone will see that there's no basis for any kind of criminal allegations," Rale said.
An inquest into Daniel Smith's death is scheduled for March 26.