A recent spate of kidnappings of U.S. citizens in the Mexican city of Nuevo Laredo and a crime wave in other border cities prompted the U.S. State Department to issue a travel alert Wednesday.
The recent violence, blamed largely on warring drug cartels, has claimed the lives of dozens of Mexicans, most of them traffickers. But American citizens are also at greater risk because of the "deteriorating security situation," the department said in a statement.
The travel alert applies only to the U.S.-Mexico border region.
In Nuevo Laredo, at least 21 Americans have been kidnapped since August, with most held for ransom, U.S. Consulate officials said. Two were killed and 10 are missing.
In Tijuana, more than 32 people have been killed this month. No Americans were among those kidnapped or killed in that city, consulate officials said.
U.S. Ambassador Antonio O. Garza Jr., in a letter to Mexican officials, worried that the crime wave would have a chilling effect on cross-border commerce.
"We certainly do not want ... to advise Americans to refrain from traveling to Mexico ... but it is our responsibility to alert them to the enhanced risks," Garza said.