(CNN) -- Mexican police have arrested another suspect in the death earlier this year of a U.S. immigration agent, authorities said Tuesday.
Jose Manuel Garcia Soto was arrested in the Mexican state of San Luis Potosi. He is thought to be involved in the death of Immigration and Customs Enforcement Agent Jaime Zapata, Mexican federal police said. Authorities said Garcia is believed to be a member of the Zetas cartel.
Last month, the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives said the weapon used to kill Zapata originated in the United States.
Zapata was killed and another agent injured February 15 when they were ambushed on a highway in San Luis Potosi. Federal authorities have offered a $5 million reward for information in the case.
The two were traveling to Mexico City in an armored car with diplomatic plates.They were run off the road and attacked from two vehicles by gunmen who opened fire indiscriminately. It was the first time in 25 years that a U.S. law enforcement agent was killed while on duty in Mexico.
The incident prompted swift action by Mexican authorities and just eight days after the shooting, they announced the arrest of the presumed leader of a group of killers allegedly involved in Zapata's killing, which was apparently carried out by mistake.
Col. Ricardo Trevilla, a spokesman for Mexico's Secretary of National Defense, said Julian Zapata Espinosa, alias "El Piolin," was the leader of the group, which he described as a cell of the Zetas drug cartel.
Trevilla said the killers were "confused by the aspects of the vehicle" in which the Immigration and Customs Enforcement agents were seated. "They thought it was owned by a rival group," Trevilla said.
CNN en Espanol's Maria Elisa Callejas contributed to this report.