Wahidur Rahman Wahid, 16, who suffered severe burns, died at 6:05am after a 30-hour battle since Friday night.

Wahid, who was undergoing treatment at ward No. 32 of Dhaka Medical College Hospital (DMCH), was having acute breathing problem despite being on artificial breathing system.

"Where'll I go now and who's going to look after me? He was feeding the family," his mother said wailing over his body.

"He broke the windowpanes of the bus and helped his elder brother Saidur out of the window after the fire caught the upper deck, but my little boy himself failed to get out."

Saidur Rahman, 25, rescued a badly-burnt Wahid when fire fighters were dousing the fire and

admitted him to the DMCH.

Unknown assailants set afire the double-decker bus at the Sheraton Hotel crossing on Friday evening that instantly burnt nine people dead and injured many.

The Detective Branch (DB) of police meanwhile was tasked with probing the arson as police remained clueless about the identity and motives of the assailants.

"We've received the order today and will have the case docket tomorrow," DB Deputy Commissioner Farooq Ahmed told The Daily Star last night.

Inspector Saud Hasan has been appointed the investigation officer (IO) of the case.

Officials at the Department of Explosives said they are sure that no explosive was used in the arson attack. "Our officers who examined the bus and gathered samples from there do not think any explosives were used to cause the fire," Nurul Islam, inspector of the Department of Explosives, told The Daily Star yesterday.

"If explosives were used, the fire would have lasted only for a few moments and have blown the roof off. Most probably, some kind of chemical or petroleum-like substance was used there," he said.

Odds are heavily stacked against gunpowder use, as it takes time to spread over an area and draws unwarranted attention, said the official.

"The easiest way to carry out such an act is to use patrol because it spreads fast in the air and instantly turns all other objects flammable," he said, adding, "We'll submit the report tomorrow or the day after."

The investigators are questioning driver of the double-decker bus Anisur Rahman, its conductor Mohiuddin and lessee Shipon. They will also quiz Shakhawat Hossain Tipu, 25, arrested from North South Road while allegedly trying to set fire to a black taxicab on Saturday.

Posing as passengers bound for Sadarghat, Shakhawat and his two accomplices hired a cab from North South Road. Immediately after getting into the car, they poured petrol and attempted to set it alight. But the driver smelt the fuel and sounded an alarm, prompting locals to catch Shakhawat.

Monwara Begum, another critically injured, was meanwhile shifted to Burns Unit of the DMCH yesterday after her condition worsened. Three other injured were also shifted there, although officials of the unit initially refused to admit them citing accommodation problem.

One Monsur Khan of Block-C in Mirpur-12 yesterday went to the DMCH morgue and claimed two unaccounted for bodies to be his wife's and daughter's. But the morgue officials did not hand over the bodies to him, as the age of his wife did not match with what he said to be.

The man, however, insisted that the bodies were of his wife Khadija Khanam, 42, and daughter Nabila Khan, 8.

Morgue officials asked him to come today and receive the body if no-one else claims them.