The events leading to the death of a U.S. Border Patrol agent in November remain a mystery, according to the FBI.
The FBI released a new report Wednesday on the case that left one agent dead and another critically injured near Van Horn, Texas. The agency said there is no evidence of an attack on the two agents.
"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 on November 18, 2017," the statement said.
Agent Rogelio Martinez, 36, died the following day from his injuries, and his partner, Stephen Garland, was critically injured.
The FBI's statement came a day after the El Paso County Medical Examiner released Martinez's autopsy report. It listed "blunt injuries to the head" as his cause of death but said the "manner of death is undetermined."
Authorities found the agents around 11 p.m. at the bottom of a culvert in the Big Bend area outside of Van Horn on Nov. 18.
They were reportedly making routine culvert checks when they were injured. Garland somehow managed to call a dispatcher and ask for help.
"To date, this investigation has not conclusively determined how Agent Martinez and his partner ended up at the bottom of the culvert and no suspects have been linked to this incident," the FBI said.
Garland was "disoriented and unsure of his location," but told the dispatcher something to the effect of “We ran into a culvert,” “I ran into a culvert,” or, “I think I ran into a culvert," the report said.
He informed the dispatcher that they were both hurt.
The dispatcher instructed Garland to activate his emergency lights to help first-responders find them.
Medics transported Martinez and Garland to an El Paso hospital where Martinez later died.
Garland has been unable to remember the details of that night.
Tips led investigators to two men, but forensic evidence determined they had no connections to Martinez's death or Garland's injuries.