Mexico migrants told to form convoys
The Mexican government has advised migrants driving home from the US for the winter holidays to form convoys for their own protection inside Mexico.
They have also been asked to travel only during daylight hours.
The interior ministry said the Mexican army could provide escorts to protect convoys from attack by criminal gangs.
Mexico's northern border states are experiencing high levels of drug-related violence, making it dangerous to travel on some major highways.
Migrants returning from the US have in the past been targeted for robbery and extortion because they often bring back new cars, cash and other goods.
The interior ministry (Segob) said returning migrants should register with Programa Paisano, a government agency which protects the rights of Mexicans who travel in and out of the country.
They can also plan their routes on its website and phone free telephone lines for advice and to report any crime against them.
"The main recommendation to travellers is to drive by day and in groups, so we suggest they go to the offices of Programa Paisano to organise caravans to be escorted and monitored", the interior ministry said.
"For its part, the Mexican army will mount an operation of intense vigilance to provide security to people travelling on the roads".
An estimated 12 million Mexicans live in the US, and the money they send home is Mexico's second-highest source of foreign income after oil exports.
The US State Department has also warned its citizens of the danger of attack while driving in northern Mexico.