A Central Bureau of Investigation team along with forensic experts on Saturday reached the premises of Gurugram's Ryan International School where the body of seven-year old Pradhyumn was found with throat slit on September 8.
The CBI sources said the 10-member team will try to gather evidence and make an attempt to recreate the events of the day Pradhyumn, a Class 2 student, was killed.
The CBI has also started questioning the school bus conductor Ashok Kumar, prime suspect in the killing, regional head of the school group Francis Thomas and HR head Jeyus Thomas after taking them into custody.
The agency had earlier approached the Protection of Children from Sexual Offences court seeking custody of Kumar, Francis and Jeyus, which was granted.
While Kumar has been sent for a one-day CBI custody, the remaining two are for two days, a CBI spokesperson said.
"At the request of the CBI in an ongoing investigation of a case related to the alleged murder of a student in a school at Gurugram, the competent court today remanded three accused in one day police custody," the spokesperson said.
The CBI had on Friday took over the probe into the killing of the seven-year-old at the Gurugram school after receiving a notification from the Centre.
The case had been registered at the Bhondsi police station in Gurugram under the Indian Penal Code section related to murder, and relevant sections of the Arms Act, the POCSO Act and the Juvenile Justice Act.
IMAGE: The accused, bus conductor Ashok Kumar, being escorted by the police. Photograph: PTI Photo
'Pradhyumn gives me the strength to fight'
Ryan murder: Child couldn't cry for help due to slashed nerve
Ryan child murder: Cops find attempts to destroy evidence
How to ensure your child's safety at school
Death could have been avoided: CBSE issues notice to Ryan school