The victim, whose parents are labourers, had gone missing while playing outside her house in Bainganwadi area last evening. The body, which bore injuries marks, was found in the dustbin in Govandi, central Mumbai, police said.
Her parents went around looking for their minor daughter and after failing to trace her, approached Shivaji Nagar Police Station, where they filed a missing person's complaint.
"Today morning a passer-by informed us that he saw a body wrapped in mattress in a dustbin. We took the body to a hospital, where it was identified," said a police officer.
Police sources said they have started detaining and questioning suspects. The crime could have been committed by a person known to the family as per the preliminary probe, they said.