Firefighters attempt to put out the flames on burning vehicles on the highway linking Mazatlan and Culiacan in Sinaloa state, as intense gunfire rocked the cartel heartland in northwestern Mexico after security forces launched an operation in which a son of jailed drug kingpin Joaquin "El Chapo" Guzman was reportedly arrested. Vehicles were set on fire and shooting shook several areas of Culiacan -- the state capital of the Guzmans' bastion, Sinaloa -- including the city's airport, an AFP reporter said. IMAGES