A senior police officer said prima facie it appeared to be a case of suicide.
The 37-year-old Tigga's body was found in the toilet of a cabin at the Alipurduar Railway Hospital.
Tigga, attached to the 969 Railway Engineer Regiment of the Territorial Army and posted at the Chalsa Railway station, was last week found tied to a post by the railway track at Deopani village and later claimed that she was abducted by unknown people.
She was admitted to the hospital after that.
"It appears to be a case of suicide. She was provided security and there were guards outside the cabin," the senior police officer said.
Her son, who was also in the cabin, raised an alarm after she did not come out of the toilet for long.
The guards found her hanging after they broke open the door to enter the toilet.
Joining the Indian Railways in 2005, Tigga successfully cleared tests to join the Railway Engineer Regiment of the Territorial Army. Six years later, she became the first woman jawan of the Indian army.
A police officer said a probe was on against Tigga following accusations that she had taken money from people on the pretext of getting them jobs.