Lawyers Vu Gia Truong, Pham Huong Giang and Le Duc Thang, representing the family of six-year-old Le Hoang Long of the Gateway International School, have requested data collected from cameras situated near the school's gate, corridors and classrooms; and for forensic analysis of the school bus where Long was found dead to find possible traces of any elements left in the bus's curtains.

They have also requested the collection of documents regarding responsibilities to pick up and drop off students of parties relevant to the case, including student monitors, teachers and communicators.

The lawyers also want statements of Long's fellow students on the bus clarified and for traces of any substance found on Long's bag to be ascertained. A medical council should be formed to analyze Long's health condition before his death, they said.

The lawyers' requests have been received and are waiting to be processed, Dinh Minh Tao, head of the Cau Giay District prosecutors department said Thursday. While some details of the investigation have already been announced, some were not clear enough for the family, he added.

Camera footage shows that on the day Long died, he did not leave the school bus to go to his classroom. Autopsy results reveal that he died between 12:30 p.m.-3:30 p.m. of respiratory failure and heat stroke, and not due to external forces, Tao said.

Additionally, bus monitor Quy had previously told the press that there was a balloon in the bus in the afternoon, when Long was found dead, but not on the morning of August 6. But the balloon was actually present on the bus since morning, according to statements of fellow students who traveled in it, said Tao.

Regarding the information that Long was wearing a gray shirt when he was found dead on the bus in the afternoon while he wore a red shirt in the morning, authorities have found the red shirt inside Long’s bag, Tao said. The red shirt has been sent for forensic analysis to look for traces, he added, without elaborating.

Long was put on the school bus on Trung Hoa Street, Hanoi's Cau Giay District at around 7 a.m. on August 6. Teachers from the school have said that Long sat on the last row of the 16-seat car, which was carrying 13 students that morning.

At around 8 a.m., school bus monitor Nguyen Bich Quy and 12 students are believed to have left the bus, leaving Long alone in it. Driver Doan Quy Phien then drove the bus to a parking lot about a kilometer away from the school, according to police investigation.

At 3:45 p.m., when the bus was driven back to the school to take the students home, Long was found motionless on the bus floor behind the driver's seat. He was rushed to hospital but the hospital said he was brought in dead.

Both Quy and Phien are being investigated for involuntary manslaughter.