The severed heads of four men have been delivered by a courier service to a police station in northern Mexico

The heads, all of men believed aged between 25-35, arrived in an icebox marked as containing vaccines. Police thought the package was meant for a local hospital, but when they opened it they found four heads. Police are investigating if the heads belong to any of the 10 local people who were recently kidnapped by gunmen. The gruesome delivery was made in the town of Ascension, not far from Ciudad Juarez, close to the US border. Ciudad Juarez has a reputation as one of Mexico's most violent cities, with more than a quarter of the country's 3,800 drugs-related murders reported to have taken place there since the start of 2008.