CIUDAD JUAREZ, Mexico (Reuters) -- The body of a woman battered to death and wrapped in a plastic bag was found on Tuesday in a Mexican border city notorious for the unsolved killings of hundreds of females in the last 10 years.

Police said they found the body of 36-year-old Micaela Felix Alvarado on an unused plot of land near her home in Ciudad Juarez, a gritty city across the border from El Paso, Texas.

"The cause of death was trauma to the skull and multiple blows. Blows to the chest, the liver and the head," Mauro Conde, a spokesman for the state attorney general's office, told Reuters.

Federal investigators in the city say 320 women have been killed here since 1993. Many were gang-raped, tortured, killed and dumped in anonymous graves.

After investigations marred by negligence and bungling, Mexican police said on Monday they were starting from scratch in their search for the killers.

The husband of the victim found on Tuesday was detained but spokesman Conde said police suspected several people were involved in the murder. He said the women was known to "associate with criminal elements" in an area of the city frequented by drug addicts and alcohol abusers. -------------Back to Zero---------

Jose Luis Santiago Vasconcelos, head of the organized crime unit in Mexico's attorney general's office, acknowledged on Monday that federal authorities were going "back to zero" in the Ciudad Juarez murder investigations.

A new team of federal and state authorities is reviewing all the case files, including reopening 67 in which suspects were convicted and sentenced, he said.

"We are reviewing them case by case," he told Reuters in Mexico City.

A group of serial killers could be responsible and they might use drugs when they commit the crimes, Santiago Vasconcelos said. Some murders could be copycat crimes, while others show evidence of family violence, he said.

Most of the victims were young, dark-skinned and unemployed or working in factories that employ women around the clock, investigators say.

The sprawling city of 2 million is home to one of Mexico's most ruthless drug cartels as well as hundreds of "maquiladora" assembly plants that mass produce goods for export and draw workers from rural Mexico, often young women.