Suspected cult leader Shai Abramof's family has not ruled out the possibility of foul play in his death, reported Army Radio on Sunday.
His lawyer said their were no previous signs that he was suicidal after having met with him on Friday morning.
The family requested that an external investigative committee be created to look into the issue of Abramof's suicide.
Abramof, 40, suspected of being a cult leader and encouraging a teacher to starve and beat her young son committed suicide in his prison cell at the Hadarim Prison in the Sharon area on Friday night.
He was found by wardens after hanging himself with a lace taken from a pair of pants. Paramedics tried to resuscitate him without success.
Abramof's two cellmates were asleep at the time of the suicide. He had undergone an evaluation by social services and found not to be suicidal, the Prisons Service said.
He was arrested in Haifa on Wednesday along with his wife on suspicion of heading the Itka cult, and ordering his followers to physically abuse their children.
Three weeks ago, a 42-year-old schoolteacher from Netanya, allegedly a member of the cult, was arrested for starving and badly beating her 10-year-old son.
Abramof's attorney, Avishag Cohen, said her client had undergone a humiliating experience during his arrest, when officers had "stepped on his head in front of his wife and children."
Cohen added that Abramof had been denied his legal rights such as consulting with an attorney following the arrest.
Last year, two inmates at Hadarim committed suicide, prompting criticism over the ability of the Prisons Service to prevent such incidents.
Assaf Goldring, who smothered his three-year-old daughter to death with plastic wrapping, leapt to his death from a jail courtyard fence in September 2009.
In August 2009, television star Dudu Topaz, arrested for ordering the beatings of television executives who rejected his ideas for television shows, took his own life. Both men were on suicide watch.
The Prisons Service set up committees to investigate the incidents. A spokesman said more than 750 suicide attempts were stopped last year.
