The US State Department has extended its travel warning for Mexico because of concern over drug-related violence.
Three more states have been added to the list of places it says Americans should avoid.
The warning says the states of Michoacan and Tamaulipas, as well as parts of Sinaloa, are all troubled by violence and organised crime.
The state department previously warned Americans against unnecessary travel to parts of the northern states of Chihuahua, Durango and Coahuila.
The BBC reports the areas affected by the warnings include popular tourist attractions such as the Copper Canyon in Chihuahua and the mountains of Michoacan, where Monarch butterflies migrate every year.