"The police have detained 20 youths and are interrogating them to identify the main accused among them," Gaya Senior Superintendent of Police Rajeev Mishra told the media.
The incident took place on Wednesday night near Sondiha village.
"The youths forcibly stopped a local doctor travelling with his wife and daughter. The doctor's hands and legs were tied and he was left in a nearby field while his his wife and daughter were gangraped," the police said.