The victim was identified as Elizabeth Muniz Tamez, aka "The Red Head," who had been charged in 2009 with belonging to a gang of kidnappers, the Public Safety Office of Nuevo Leon state, where Monterrey is located, said in a statement. Her hair had been dyed blond when the body was found.
Muniz Tamez escaped from custody Monday, when a group of armed assailants snatched her from a prison vehicle taking her for medical treatment.
A doctor, two prison officials and three guards have been detained and are under investigation in the escape.
There was no immediate evidence of drug cartel involvement in the death of Muniz Tamez, who was found hanging by a rope. But Monterrey, Mexico's third-largest city, has been rocked by violent cartel turf battles in recent months.
She was wearing only jeans and socks when found just before dawn, and someone had scrawled the man's name "Yair" on her naked torso, the Public Safety Office said. Her identity was determined through fingerprints.
Mexico's former top anti-drug prosecutor, Samuel Gonzalez, said the killing "was totally outside the normal range" of the usual behavior of Mexico's criminal gangs.
"They have totally changed the rules," Gonzalez said in a telephone interview with The Associated Press. While he noted that the wives of top drug traffickers have been targeted for killings in the past, he said women were largely spared the country's rising level of drug violence until a few years ago.
As of November, drug-related violence had claimed the lives of 30,196 people in Mexico since the government launched an offensive against drug cartels in December 2006.