Investigators have told NBC News that they cannot rule out the possibility that Border Patrol agent Nicolas Ivie, who was shot to death Tuesday morning, may have been a casualty of "friendly fire." NBC's Mark Potter reports.

Federal investigators have told NBC News they are examining whether the shootings of Border Patrol agents early Tuesday morning were the result of friendly fire – officers accidentally shooting each other.

Initial reports from U.S. and local officials blamed the shootings on armed criminals. Agent Nicholas Ivie, 30, was killed and another agent was wounded in the incident.

Mexican police said Thursday that they arrested two suspects in a Mexican military operation in the city of Agua Prieta, in Mexico’s northern Sonora state, a few miles from where Ivie was shot, Reuters reported.

Related: Mexican troops arrest two in killing of US border agent

Ivie was responding to desert sensors that track movements in a remote area five miles north of the U.S.-Mexico border, near Naco, Ariz., authorities have said. He was with two other agents, one of whom was wounded and released from the hospital after undergoing surgery. The third agent, a woman, was unharmed.

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

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, an attempt to track the weapons.

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

Regarding the more recent case, investigators caution that that have reached no conclusions and still have lots of work to do. But they said they cannot rule out that it was a friendly fire incident.

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