MEXICO CITY (Reuters) - Violence at a prison on the outskirts of Mexico's northern business city Monterrey killed at least 20 people on Sunday, authorities said.
A fight broke out in the early hours of Sunday morning between guards and prisoners, who started a fire by setting mattresses alight, a government spokesman told Mexican television news.
The prison was later secured, the spokesman told television channel Milenio.
Powerful drug cartels are fighting for control of smuggling routes along the U.S.-Mexico border and rivalries often spread into the prison system, where prisoners held on federal drug charges are mixed with common criminals.
A fight between rival gangs in another prison in the north of the country left 31 inmates dead in January and a further 13 wounded.
About 50,000 people have died in Mexico in the past five years since President Felipe Calderon launched a frontal attack on drug gangs. Packed and inefficient prisons are plagued with corruption and mass escapes.
(Reporting by Adriana Barrera and Elinor Comlay; Editing by Sandra Maler)