"The girl, Kirti Navrath slipped and fell in the nullah near Ram Mandir on Yeoor hills this afternoon and got washed away," Santosh Kadam, officer-in-charge of the Regional Disaster Management Cell, Thane Municipal Corporation (TMC) told PTI.
The victim was part of a group of 35 students and three teachers of Samruddhi Classes of Sambaji Nagar of the city, who had gone for a picnic to the hills.
A rescue team comprising local firemen, divers and police have launched a search operation, though the girl is yet to be traced, police said.