RIO GRANDE VALLEY — U.S. Border Patrol agents in the Valley have seized more than $12.6 million dollars worth of narcotics in the last four days. The largest seizure was made on Friday at the Falfurrias checkpoint on Highway 281 when a K-9 detected the odor of marijuana coming from a tractor trailer. In a similar seizure, at the Sarita checkpoint on highway 77, agents found more than 2,600 pounds of marijuana and then another occurred near La Rosita on Sunday.