Federal investigators said Friday that preliminary findings indicated that the fatal shooting of one U.S. Border Patrol agent and the wounding of another in southern Arizona this week was the result of friendly fire.

“While it is important to emphasize that the FBI’s investigation is actively continuing, there are strong preliminary indications that the death of United States Border Patrol Agent Nicholas J. Ivie and the injury to a second agent was the result of an accidental shooting incident involving only the agents,” FBI Special Agent James L. Turgal Jr. said in a statement.

Ivie, 30, a native of Utah, was responding to a sensor alarm in the desert 100 miles southeast of Tucson on Tuesday at the time of the shooting. At least two other agents were involved in the incident.

The Mexican Embassy in Washington said Thursday that Mexican authorities had arrested two suspects in the shooting. Law enforcement officials said Friday that the pair have no prior criminal records and that it was unclear whether they were involved in the incident. Investigators have not recovered any guns from the scene.

Ivie was based at a border station named in honor of Brian Terry, an agent who was shot dead in December 2010 and whose killing gained national attention after it was linked to the flawed “Fast and Furious” gun-tracking operation run by the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Homeland Security Secretary Janet Napolitano on Friday visited the Border Patrol station and met with Ivie’s family.

Steve Vogel contributed to this report.