The police chief of Praxedis G. Guerrero, a city in the northern Mexican state of Chihuahua, her husband and son are in critical condition after a knife attack staged by masked men, prosecutors said.

Rosario Rosales Ramirez and her relatives were "wounded with sharp weapons in several parts of the body" on Wednesday, the Chihuahua state Attorney General's Office said.

The 40-year-old Rosales took over on May 31 as police chief of Praxedis G. Guerrero from Marisol Valles, who fled to the United States in March and requested political asylum after receiving death threats from drug traffickers.

Praxedis G. Guerrero is one of the most violent cities in northern Mexico and several police officers have been killed there.

Valles garnered headlines after she decided to apply to be chief of the police department in October 2010 at age 20 when no one else dared take up the post.

The assailants who attacked Rosales and her family stole two vehicles and several electric motors from the police chief's residence, the AG's office said.

Praxedis G. Guerrero is in the Juarez Valley, on the banks of the Rio Grande, an area where drug cartels have been battling for control of smuggling routes into the United States.

Chihuahua is Mexico's most violent state and home to Ciudad Juarez, a gritty border metropolis located across the border from El Paso, Texas, where more than 900 people have died in drug-related violence this year.

The northern state has accounted for about 30 percent of the more than 40,000 murders committed in Mexico since late 2006, when President Felipe Calderon declared war on Mexico's drug cartels.

More than 8,500 killings have occurred in Ciudad Juarez alone during since the end of 2006.