A 21-year-old undertrial lodged in the Ambala Central Jail hanged himself to death from a tree on the jail premises, just a day after he was sent to judicial custody for allegedly abducting a class 11 girl, police said on Wednesday. Gurmeet Singh (21), a resident of Yamunanagar, was arrested recently on the charges of abducting the girl student from Panjokhra village and was sent to judicial custody on Monday, they said.