The Jharkhand Sampark Kranti Express was stopped late last night at the railway station here and the girls, some of whom were minors, were made to get down and questioned, SSP Nitin Tiwari said.
The arrested persons are being interrogated, he said.
The minors have been handed over to Child Welfare Committee, while the elder girls were allowed to leave, he said.
Kumar Gaurav of NGO Ashadeep foundation, which accompanied the police, said information had been received from Kanpur Childline that about 20 girls were going to be trafficked.
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They said they are from Ranchi in Jharkhand and claimed that they were going to meet some relatives.
Some of the girls' relatives came to pick them up later, the SSP said.
CWC Chairman said all aspects of the case were being probed.
None of the girls have lodged any complaint.