A Border Patrol agent whose death last November fueled President Trump’s calls for a border wall appears to have died in an accident, according to FBI findings released Wednesday.

Border Patrol Agent Rogelio Martinez, 36, was found dying at the bottom of a roadside culvert along a span of Interstate 10 in West Texas on Nov. 18. Within hours, union officials said they believed Martinez had been ambushed by smugglers in a rock attack.

The agent’s death became a political flash point less than a day later when Trump tweeted that Martinez had been “killed” and that his assailants would be brought to justice.

But the FBI said it has found no evidence of a homicide, despite mobilizing significant resources involving 37 field offices to investigate Martinez’s death.

“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 report said.

“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 report added.

An autopsy report released Tuesday by the El Paso County Medical Examiner’s Office confirmed that Martinez died of blunt injuries to the head, but it listed the manner of death as “undetermined.”

Another agent, Stephen Garland, was also found injured nearby with serious head injuries and other trauma. Investigators have said he cannot recall details about what happened.

But the FBI findings include previously undisclosed details about the moments immediately after the agents were injured and Garland radioed for help.

In his distress call, Garland told the dispatcher: “We ran into a culvert,” “I ran into a culvert” or “I think I ran into a culvert,” the report said.

In the course of its investigation, the FBI said, it identified several individuals in New Mexico with potential ties to the case. They have been charged with offenses involving the “smuggling of an alien,” but the agency said they are not suspects in the investigation of Martinez’s death.

Judy Melinek, a San Francisco forensic pathologist who reviewed Martinez’s autopsy report at the request of The Washington Post, said the injuries described in the report were more consistent with an accident or fall than an assault.

Melinek stressed that the report contains limited information, and she didn’t have access to photos, X-rays and other materials available to the El Paso medical examiner who performed the autopsy.

“He doesn’t have injuries on his back and front. He doesn’t have injuries on both sides of his body. They are all on the right side and in line with each other. There are also no defensive injuries on the arms or hands,” she said. “The absence of defensive injuries and a single plane of injury is more consistent with an accident than a homicide.”

Backers of Trump’s plans for a border wall have continued to insist Martinez was murdered and challenged others who have cast doubt on the version of the event advanced by union officials.

Chris Cabrera, a spokesman for the National Border Patrol Council, which represents agents, said his union continues to believe that Martinez and Garland were attacked.

“We believe it was an assault on our agents and a murder of one of our agents and an attempted murder of another,” he said.