PHOENIX (AP) — Friendly fire likely was to blame in a shooting near the Arizona-Mexico line that killed one federal agent and wounded another, the FBI said, noting the investigation was still ongoing in the case that reignited the political debate over border security.

"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 in Charge James L. Turgal Jr. said in a statement Friday.

Turgal didn't elaborate on its conclusions but said the FBI is using "all necessary investigative, forensic and analytical resources as it investigates the Tuesday shooting about five miles north of the border near Bisbee.