A border patrol agent whose death Donald Trump has invoked to build support for a border wall was likely not killed in an attack, the FBI said.

Last November two injured border patrol agents were found with traumatic head injuries in a culvert in Texas, the FBI said. One of them, Rogelio Martinez, died of his wounds.

The President responded to news of Mr Martinez’s death by saying he had been “killed” and then urging the construction of a wall spanning the US-Mexico border, which he has cast as a necessary security measure.

“We will, and must, build the Wall!” Mr Trump said.

But an update from the FBI on its investigation complicated the picture. El Paso Special Agent in Charge Emmerson Buie said in a statement that his office investigated multiple explanations, including whether Mr Rogelio was “ambushed or attacked”. They have found no evidence to support that.

“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,” Mr Buie said.

Life on the US-Mexican border Show all 12 1 /12 Life on the US-Mexican border Life on the US-Mexican border Tijuana, Mexico A house stands next to a section of the border fence separating Mexico and the US Reuters Life on the US-Mexican border Tijuana, Mexico The border fence in Tijuana stretches all the way to beach Reuters Life on the US-Mexican border Tijuana, Mexico Migrants can often be spotted trying to cross the rusty barrier Reuters Life on the US-Mexican border Tijuana, Mexico Joaquin, 36, a chef from Guatemala who says he was deported from the US Reuters Life on the US-Mexican border Tijuana, Mexico A shack stands next to a section of the border fence Reuters Life on the US-Mexican border Tijuana, Mexico Tourists pose for a picture at the border Reuters Life on the US-Mexican border Tijuana, Mexico A family burns rubbish near the fence Reuters Life on the US-Mexican border Tijuana, Mexico Joaquin makes a living by selling rubbish Reuters Life on the US-Mexican border Tijuana, Mexico ‘Neither Trump nor the wall is going to stop anyone,’ says Pedro Reuters Life on the US-Mexican border Tijuana, Mexico Mexicans have built homes right next to the fence Reuters Life on the US-Mexican border Tijuana, Mexico Mexican Carlos, 27, who says that he was deported from the United States, heats up tortillas at his house near the double fence that separates Mexico and the US Reuters Life on the US-Mexican border Tijuana, Mexico A girl climbs stairs near a section of the fence

Shortly after Mr Martinez’s death, Culberson County Sheriff Oscar Carrillo cast doubt on the notion that the agent had died in an attack.

“If this was an assault, believe me, as sheriff, I’d be the first one out there emphasising safety in our community and with our deputies, pairing them up,” Mr Carrillo told the Dallas Morning News.