RGV becoming a top trafficking corridorBorder Patrol: Upper Valley shows increase in drug seizures, undocumented immigrant arrests.BY ANGELES NEGRETETHE BROWNSVILLE HERALDThe Rio Grande Valley is becoming a top corridor along the U.S.-Mexico border for illegal immigration and drug trafficking, U.S. Border Patrol officials said Wednesday.Federal officials say the most active portion of the corridor is between McAllen and Rio Grande City, where about 1,700 undocumented immigrants were arrested this month and more than 4,000 pounds of marijuana were confiscated.In Brownsville, agents arrested only 516 undocumented immigrants and seized 29 pounds of marijuana this month, said Reynaldo Diaz, Border Patrol spokesman for the McAllen sector.The 2004 averages also support beliefs that illegal smuggling operations are concentrated in the upper Valley. Agents in the Brownsville area arrest about 17 people daily for illegal entry into the United States, compared to about 98 in McAllen and 25 in Rio Grande City.“Currently what we’re seeing is an increase in the arrests of undocumentedPLEASE SEE CORRIDOR, A12