The father, mother and maternal aunt of two deceased siblings in the capital's Banasree, are being brought to Dhaka from Jamalpur by the RAB for interrogation.
The RAB officials are on the way to Dhaka with the trio, RAB's Media and Legal Wing Director Commander Mufti Mahmud Khan.
The siblings -- Nusrat Jahan, 14, and Alvi Aman, 6 -- were buried in Jamalpur on Tuesday.
Autopsy findings suggests that the two deceased siblings who were initially thought to have died from food poisoning in the capital’s Banasree, might have actually been strangled to death.
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The siblings died at Dhaka Medical College Hospital on Monday night, hours after they ate food bought from a Chinese restaurant.
DMC forensic department Lecturer Dr Prodeep Biswash, who conducted autopsies of the siblings, told journalists that both children had injury marks on their throats. Nusrat also had blood in her eyes and Alvi had injury marks on one of his legs.
However, the cause of death can only be confirmed after result from the viscera test comes in, the doctor added.
On late Monday night, police arrested Masud Rahman, the manager of Kent Chinese Restaurant from where the food was bought, the restaurant’s head chef Asaduzzaman Rony and his associate Ataur Rahman, said Inspector (investigation) Mostafizur Rahman of Ramna police station.
Rapid Action Battalion also detained three more people: Obaidur, a relative of Nusrat and Alvi; Sheuly, the private tutor of the children; and Pintu Mondol and Ferdous, two security guards of the building the children lived in.
RAB sources said they were detained for interrogation on Tuesday afternoon.
No case was filed with the police station concerned as of Wednesday morning.