Updated at 8:20 p.m. ET: MEXICO CITY -- Mexican troops have arrested two suspects in the killing of a U.S. Border Patrol agent and the wounding of a second officer in Arizona, Mexican security officials said on Wednesday. 

The two suspects were detained in a Mexican military operation in the city of Agua Prieta, in Mexico's northern Sonora state, a few miles from the spot where Nicholas Ivie was shot dead early on Tuesday while responding to a tripped ground sensor, a Mexican Army officer, who declined to be named, told Reuters.

Ivie was among three agents who were patrolling on foot about five miles north of the international border when gunfire erupted. A second agent was also wounded while the third, a woman, was unharmed.  

The agents had been patrolling in an area near the border town of Naco, well-known as a corridor for smuggling, and the Cochise County Sheriff's department has said that tracks were found heading south after the shooting.

Related: Feds examine whether friendly fire killed border agent

Ivie was a 30-year-old father of two who grew up in Utah and was active in the Mormon Church. He had been an agent for four years.

A Mexican police official in Naco, across the border from the Arizona town of the same name, confirmed the arrests, which occurred in the early hours of Wednesday.

U.S. officials refused to comment on the report of the arrests to NBC News.

It was the first fatal shooting of an on-duty Border Patrol agent since December 2010, when Brian Terry was killed in a shootout with bandits near the border. Terry's shooting was later linked to the government's "Fast and Furious" gun-smuggling operation, which allowed people suspected of illegally buying guns for others to walk away from gun shops with weapons, rather than be arrested.

Two Border Patrol agents were killed last year in an accident during a car chase with smugglers near Phoenix.

Reuters and The Associated Press contributed to this report.

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U.S. Customs and Border Protection / AP file

U.S. Customs and Border Protection agent Nicolas Ivie, 30, who was shot to death early Tuesday near the U.S.-Mexico line in Arizona.

U.S. Customs and Border Protection has identified an agent who was shot to death near Naco, Arizona early Tuesday as 30-year-old Nicolas Ivie, a native of Provo, Utah who has been with the federal agency since 2008, KVOA.com in Tuscon reported.

A news release from Customs and Border Protection said that Ivie and two other agents were responding to a motion sensor that was activated along the border. Another agent, whose name was not released, sustained non-life-threatening injuries and was in stable condition after being airlifted to a local hospital.

The agents who were shot were on patrol with a third agent who was not harmed, George McCubbin, president of the National Border Patrol Council, a union representing about 17,000 border patrol agents, told The Associated Press.

In a statement issued Tuesday CBP Deputy Commissioner David Aquilar said the agency suffered the loss of Ivie "at the hands of criminals operating on the border near Naco, Arizona."

"Agent Ivie died in the line of duty, protecting our nation against those who threaten our way of life," he said. "His death only strengthens our resolve to enforce the rule of law and bring those responsible to justice. Our thoughts and prayers are with Agent Ivie’s family and friends in this difficult time.”

The FBI, which is investigating the shooting with the Cochise County Sheriff's Office, said in a press briefing Tuesday afternoon that they had deployed a special group of agents from Phoenix to process the crime scene.

See coverage at KVAO.com

Authorities did not say whether investigators had recovered guns or bullet casings at the site.

No arrests have been made, but authorities suspect that more than one person fired at the agents.

"It's been a long day for us but it's been longer for no one more than a wife whose husband is not coming home. It's been longer for two children whose father is not coming home, and that is what is going to strengthen our resolve" to find those responsible and enforce the law, said Jeffrey Self, commander of Customs and Border Protection's Arizona joint field command.

The shooting occurred at a patrol base about 100 miles southeast of Tucson named after Brian Terry — a border agent who was killed in December 2010 in an incident at the center of a controversy over a Bureau of Alcohol, Tobacco and Firearms and Explosives (ATF) gun tracking operation known as "Fast and Furious."

Brian A. Terry Border Patrol Station dedicated for slain agent

The operation allowed people suspected of illegally buying guns for others to walk away from gun shops with weapons, rather than be arrested.

Authorities intended to track the guns into Mexico. Two rifles found at the scene of Terry's shooting were bought by a member of the gun-smuggling ring being investigated.

Critics of the operation say any shooting along the border now will raise the specter those illegal weapons are still being used in border violence.

Twenty-six U.S. Border Patrol agents have died in the line of duty since 2002, the AP reported.

Feds reveal more charges in murder tied to 'Fast and Furious'

NBC News' Kari Huus and The Associated Press contributed to this report.

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