The victim, a resident of Bolrampur village in neighbouring Bengal, was found lying unconscious by a roadside, with several injuries on her, by a team of National Disaster Response Force late Monday in Bihta, about 30 km from Patna, a police official said.
Patna Senior Superintendent of Police Manu Maharaj said the Bengali speaking woman in her early 30s was gangraped.
"Gang rape was confirmed by her medical examination at a local hospital," he said.
She was admitted to a government hospital. "With the help of a mason, who was working near the hospital, she informed the police that four-five people gangraped her," police said.
The woman told police that she parted from her husband at the Howrah railway station in Kolkata, and boarded a train.
Police have lodged a case and begun investigations as to how she reached Bihta from Kolkata.
No arrests have been made so far, police said.