The two siblings in Banasree might have been suffocated to death as injury marks were found in their necks and other parts of their bodies.
DMCH Forensic department lecturer Prodeep Biswash, who conducted the autopsy of the siblings, told the reporters that they found the symptom of suffocating the siblings to death.
He, however, said they can confirm the reason of the deaths after getting viscera report.
The duo -- Nusrat Jahan, 14, and Alvi Aman, 6, died at Dhaka Medical College Hospital on Monday night, hours after they ate food bought from a Chinese restaurant.
Their mother Mahfuza Malek Jesmin said the family brought home leftover food after having dinner on Saturday night at a Chinese restaurant near their Banasree home.
The mother served the rest of the Chinese food to her two children for lunch on Monday while she and her husband had a home-cooked meal.
Both children were rushed to the Dhaka Medical College Hospital after the mother noticed that they were not waking up from an afternoon nap.