Inmates armed with bats and blades brawled and ignited a fire in a packed prison in northern Mexico on Thursday, leaving 49 dead in the bloodiest jailhouse riot in years.

Inmates armed with bats and blades brawled and ignited a fire in a packed prison in northern Mexico on Thursday, leaving 49 dead in the bloodiest jailhouse riot in years.

Twelve others were injured during the battle that lasted 30 to 40 minutes at the Topo Chico prison in the industrial city of Monterrey, said Nuevo Leon state Governor Jaime Rodriguez.

The fight erupted following a dispute over control of the prison between two rival members of the Zetas drug cartel, Rodriguez said.

"They used sharp weapons, bats, sticks," the governor told radio Imagen, adding that the 60-year-old penitentiary houses 3,800 inmates, overseen by 100 guards.

The National Human Rights Commission says the prison has room for 3,635 convicts.

One of the inmates was shot dead by a prison guard who was protecting a group of women, Rodriguez said.

During the brawl, inmates set a fire in a supply room and TV images showed flames coming out of the prison in the middle of the night.

The riot erupted on the eve of Pope Francis' five-day trip to Mexico, during which he is due to visit another notorious prison in the northern border city of Ciudad Juarez.

Five of the injured inmates were in serious condition, and none of those involved in the riot managed to escape.