From the AP:

The Mexican government warned its citizens Tuesday to use extreme caution if visiting Arizona because of a tough new law that requires all immigrants and visitors to carry U.S.-issued documents or risk arrest.

President Barack Obama also criticized the law, saying it could lead to harassment of Hispanics, and he called for bipartisan support to fix America’s broken immigration system. Two senior officials in his government said the Arizona law may face a legal challenge by federal authorities.

“Now suddenly if you don’t have your papers, and you took your kid out to get ice cream, you’re going to get harassed — that’s something that could potentially happen,” the U.S. president said of the measure. “That’s not the right way to go.”

Arizona’s law — slated to take effect in late July or early August — makes it a state crime to be in the U.S. illegally and allows police to question anyone they suspect of being an illegal immigrant. Lawmakers said the legislation, which has sparked huge protests and litigation, was needed because the Obama administration is failing to enforce existing federal laws.

Mexico’s Foreign Ministry issued a travel alert for Arizona after the law was signed, warning that its passage shows “an adverse political atmosphere for migrant communities and for all Mexican visitors.”

The alert said that once the law takes effect, foreigners can be questioned at any moment and detained if they fail to carry immigration documents. And it warns that the law will also make it illegal to hire or be hired from a vehicle stopped on the street.