* Agent killed, another hurt in pre-dawn shooting
* Homeland Security secretary meets with agent's family (Adds biographical details about Ivie)
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" from the ongoing investigation.
Before daybreak on Tuesday, Nicholas Ivie was one of three agents responding on foot to a tripped ground sensor, in a well-known smuggling corridor, when gunfire erupted.
They were a few miles north of the border, near the tiny border town of Naco. A second agent was wounded in the incident, but has since been released from the hospital, and the third agent was unharmed.
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.
"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.
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.
Ivie, 30, had been an agent for over six years, Self said.
On Thursday, Chris Ivie told reporters that his brother once came across a pregnant woman near the border, her feet badly cut up and wrapped in rags, and that Ivie carried her a mile and a half (2.4 km) to receive help.
Ivie, who had a wife and two daughters, was a Mormon who learned Spanish during a two-year church mission to Mexico, a spokesman for the family said in a statement. Ivie's family on Monday will hold a funeral in Sierra Vista, Arizona, where he lived, and the service will be open to the public.
Matthew Benson, a spokesman for Arizona Republican Governor Jan Brewer, on Friday defended her comments made soon after the shooting, in which she criticized the federal government for inaction on securing the porous border with Mexico.
"The governor does not make statements lightly on something like this," Benson said. "Her initial remarks were based upon the best information available at the time from law enforcement. Whether this was a friendly fire incident or not, that does not change the tragedy that has occurred here."
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, the 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.
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."