Art Del Cueto, national spokesman for the union, said Wednesday the FBI's comments were preliminary.
The incident happened last November.
Border Patrol pallbearers carry Border Patrol agent Rogelio Martinez to a graveside service at Restlawn Cemetery, Saturday, Nov. 25, 2017 in El Paso, Texas. "To date none of the more than 650 interviews completed, locations searched, or evidence collected and analyzed have produced evidence that would support the existence of a scuffle, altercation, or attack".
Garland was disoriented and unsure of his location but knew he and Martinez were badly hurt and needed help. Investigators said Garland made a statement to the effect of "We ran into a culvert", "I ran into a culvert", or "I think I ran into a culvert".
The agents were patrolling in separate vehicles and it's unclear why both ended up at the culvert, according to the Border Patrol.
Martinez's death was immediately seized upon by members of the Republican Party.
The National Border Patrol Council, which endorsed Trump's presidential bid, took it one step further, asserting - seemingly without any evidence - that Martinez had been stoned to death by undocumented immigrants. We will seek out and bring to justice those responsible. "We will, and must, build the Wall!".
Sen. Ted Cruz (R-Texas) also described both agents as having been "attacked" and suggested that it was the result of an "unsecure border".
The FBI continues to offer a reward of up to $50,000 for information on the case and provides this number: 915-832-5000 to call with information.
The mystery surrounding the death of US Border Patrol agent Rogelio "Roger" Martinez is nowhere close to being solved.
Martinez was patrolling near Van Horn, Texas, with his partner, Stephen Garland, when authorities said Garland radioed for help on the night of November 18.
He pointed to the lack of injuries on the lower part of Martinez's body.
The FBI said the investigation is ongoing.
Martinez's fiancée, Angie Ochoa, said she believes the autopsy report is cover-up.
There's been much speculation about whether the agent was ambushed or if his death was an accident.
Concentrated investigative activities and canvasses for witnesses and evidence have taken place across the United States. Investigators also talked to six employees of Union Pacific Railroad, which had locomotives in the area.
"To date, none of the more than 650 interviews completed, locations searched, or evidence collected and analyzed have produced evidence that would support the existence of a scuffle, altercation or attack", the agency said in a statement, referring to the incident on November 18. They have found no evidence to support that.
"The absence of evidence is a key factor in this case - not due to lack of effort or determination, but because evidence which would indicate the presence of other persons or the commission of a criminal act is not present", the memo reads. The El Paso medical examiner's office found that Mr. Martinez, 36, had died of blunt injuries to the head, but could not determine the manner of death. A forensic analysis, though, determined that neither had anything to do with the attack. The defendants are innocent until proven guilty in a court of law.
The Federal Bureau of Investigation said it's found no evidence that two U.S.