The CID will speak to Tithiswar Baidya’s friends and those who attended coaching classes with him for clues to the Class XII student’s death.

The teenager, who had topped Jodhpur Park Boys’ School in Madhyamik, received a call on his cellphone at 9pm on October 19, less than an hour before his body was found with his head and an arm severed on railway tracks near Ballygunge, said a CID officer. The boy had left home after receiving a phone call around 7pm. His mother had also called him around 9pm.

The agency declined to reveal who had called him at 9pm. “We have a name but that does not prove anything. We need to identify those who were close to Tithiswar. Then we would check the call details and speak to those who used to study with him in coaching classes,” added the officer. One of Tithiswar’s two cellphones is missing.

On October19, the driver of a train had informed the Lake Gardens stationmaster that it had hit someone at 9.38pm.