Limpopo police are still hunting down those who threw what is believed to be a petrol bomb at a house outside Mokopane, killing three of the eight people who were asleep inside.
The family, aged three months to 70 years, were trapped after their Sekgakgapeng village house immediately caught alight in the early hours of Friday, Colonel Moatshe Ngoepe said on Tuesday.
She said firefighters managed to extinguish the flames but it was too late for five-year-old Kamogelo Kekana, who died on the scene.
Her two-year-old sister, Sadie Kekana, died on the way to hospital.
Ngoepe said their grandfather, Hendrick Kekana, 64, died while he was admitted in hospital for serious burn wounds.
"The motive behind this incident is still unknown at this stage but domestic violence may not be ruled out."
Cases of murder, attempted murder and arson are being investigated.
Ngoepe said a special joint task team was hot on the heels of the suspect.
"The police are still calling upon Bongani Abrahm Boshomane aged 45... to report at Mahwelereng or the nearest Police Station to assist them [with] the ongoing investigations."
Anyone with information that could lead to an arrest should contact Brigadier Mokgaetsi Malahlela on 082 415 5436 or Crime Stop on 08600 10111 or the Crime SMS line on 32211.