Police are examining whether the girl was abducted and murdered or it was a case of accidental death.
The girl's body has been sent for post mortem examination and the possibility of sexual assault cannot be ruled out at this stage, a senior police official said.
Prima facie there are no external injuries on the body, said the official, adding that several locals have been questioned.
"The girl was missing since last evening and a missing complaint was lodged by her parents. A thorough search was conducted in the area following which a case under Section 363 of IPC was registered," said DCP(west) Pushpendra Kumar.
The girl's body was spotted this morning in the drain around half kilometre away from slum cluster where her family lives. The locals staged a protest over death of the girl outside the police station.