Dozens of people have been killed in a prison riot in Mexico, just days ahead of a planned visit by Pope Francis to another of the country’s notoriously dangerous and overcrowded jails. At least 50 inmates and guards are thought to have been killed in the disturbance at the Topo Chico prison in Monterrey. Relatives of inmates who went to the site when they learnt of the incident said they heard gunshots in the early hours. Smoke was seen billowing from the building as police sealed off the streets nearby. They suspect some inmates may have escaped. The riot erupted on the eve of Pope Francis’ trip to Mexico, during which he will visit another notorious prison in the northern border city of Ciudad Juarez.