The Consulate General in Matamoros issued on April 8, 2011 a new warden message warning of possible threat to American citizens in three consular districts. Excerpt below:
The United States Consulates General in Matamoros, Nuevo Laredo, and Monterrey advise American citizens that the U.S. government has received uncorroborated information that Mexican criminal gangs may intend to attack U.S. law enforcement officers or U.S. citizens in the near future in Tamaulipas, Nuevo León and San Luis Potosi. This information is being distributed to all U.S. government employees in the three states. No other information is available. If more detailed information is developed, we will advise American citizens immediately.
Matamoros (the southern part of Tamaulipas with the exception of the city of Tampico): Avenida Primera 2002, telephone (011)(52)(868) 812-4402. http://matamoros.usconsulate.gov/.
Monterrey (Nuevo Leon, Durango, Zacatecas, San Luis Potosi, and the southern part of Coahuila): Avenida Constitucion 411 Poniente, telephone (011)(52)(818) 047-3100. http://monterrey.usconsulate.gov/.
Nuevo Laredo (the northern part of Coahuila and the northwestern part of Tamaulipas): Calle Allende 3330, col. Jardin, telephone (011)(52)(867) 714-0512. http://nuevolaredo.usconsulate.gov/.
Read in full here.