The girl's body was found near a water body at Kirtipur with indications that she was killed after being raped, the sources said.
Her parents had informed the police after she did not return home from college last evening.
The sources said the girl was suspected to have been taken away by miscreants after she alighted from a bus on her way home from college.
Local people alleged had the police acted in time after receiving complaints from the parents, the girl could have been rescued.
A mob set up a road blockade on the Kharibari-Rajarhat road at Barasat in the district halting traffic for several hours and stoned vehicles including two police jeeps, police sources said.
A mob gheraoed Trinamool Congress MP Nurul Islam and damaged his car and demonstrated before Food Minister Jyotipriya Mullick when they went to the area.
The Food Minister promised proper policing and a police camp in the area.
The incident came a day after three TV reporters were attacked and injured by men carrying Trinamool Congress flags in the same district allegedly as a fallout of infighting in Trinamool Congress.
Three TV reporters who went to the spot were assaulted with iron rods and lathis.
