The U.S. Border Patrol arrested a Mexican immigration official who was allegedly trying to help a group of undocumented migrants sneak into the United States, the Mexican government said Sunday.

Immigration agent Francisco Javier Gutierrez was arrested at a checkpoint near Alamogordo, N.M., about 100 miles north of the U.S.-Mexico border, the Mexican Interior Department said in a news release.

Gutierrez had been fired on corruption allegations last year but returned to his job after winning a court case in which he claimed he had been unfairly dismissed, according to the National Immigration Institute.

The Mexican government promised to cooperate with U.S. authorities in the case. A spokesman for the Border Patrol in El Paso, Texas, declined to comment Sunday.

Gutierrez's arrest comes just days after the Mexican and U.S. governments exchanged terse diplomatic notes about security on the border.

Last Monday, men dressed in Mexican military-style uniforms unloaded what appeared to be bundles of marijuana before setting fire to an SUV in the Rio Grande as Texas law enforcement officers watched from the other side of the river.

Mexican officials have said the men were not Mexican soldiers. Texas authorities have said they want to investigate the incident further.

U.S. Ambassador to Mexico Tony Garza sent a note to the Mexican government two days later urging it to clamp down on drug-related violence and corruption on the border region. Mexican Foreign Secretary Luis Ernesto Derbez responded by calling Garza's comments out of line and sending his own diplomatic note asking the ambassador to stop making public comments about security and immigration issues.

Garza then sent a second note Friday, reiterating a request "that the Government of Mexico undertake additional measures to prevent cross-border violence and to provide our government with any investigative results they may have related to the violence."

Also last week, a tunnel was discovered running about 2,400 feet from a warehouse near the airport in Tijuana to a warehouse in San Diego. More than 2 tons of marijuana had been found inside. It was unclear how long the tunnel had been in operation.