(Reuters) - Friendly fire probably killed a U.S. Border Patrol agent in Arizona near the Mexican border this week, the FBI said on Friday, citing "strong preliminary indications."
Nicholas Ivie was one of three agents patrolling on foot about four miles (eight km) north of the border before daybreak on Tuesday when gunfire erupted as the agents responded to a tripped ground sensor, authorities have said.
A second agent was wounded in the incident near the town of Naco, an area known as a smuggling corridor. The third agent was unharmed.
"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," the FBI said in a statement.
Ivie was the fourth Border Patrol agent to die in violent circumstances in less than two years in Arizona. His death heightened concern about border security in a state at the forefront of the national immigration debate.
Commander Jeffrey Self of the Customs and Border Protection's joint field command in Arizona told reporters he met with the Ivie family on Friday about the possibility the shooting was a "tragic accident, the result of friendly fire."
U.S. authorities had previously released scant details about the circumstances of the shootings.
The agents were tracking footprints before the incident, said Carol Capas, spokeswoman for the Cochise County Sheriff's Office, which has jurisdiction over the area and is investigating the shootings along with the FBI.
Mexican officials said two men were arrested this week in a military operation near the city of Agua Prieta, a few miles across the border from the shooting scene.
U.S. authorities have declined to comment on those arrests. Capas said her office had not been officially notified of any arrests.
U.S. Homeland Security Secretary Janet Napolitano, a former Arizona governor, held talks with law enforcement officials on Friday at the Border Patrol station where Ivie worked.
Kevin Goates, an Ivie family spokesman, declined to comment on the FBI announcement of the preliminary findings in the case.
He said Napolitano had met with Ivie's widow, Christy, and other family members for about 40 minutes at her home in southern Arizona.
Self delivered a message to Christy Ivie when he spoke to reporters.
"Christy, today we know that in the uncertainty of darkness the conditions were set and the hand of God brought Nick home," he said. "Know we will always honor his memory."