The FBI said it is investigating the death of Border Patrol agent Rogelio Martinez as "a potential assault of a federal officer," but the agency cautioned Tuesday it has not reached any conclusions as to what happened over the weekend along a desolate span of Interstate 10 in West Texas, reports the Washington Post.

"We call it potential because we do not yet have the full picture yet as to what transpired," FBI Special Agent-in-Charge Emmerson Buie Jr. said at a news conference at El Paso's FBI offices, about 135 miles west of the drainage culvert where Martinez and another agent were found badly injured late Saturday.

Martinez, 36, who died of devastating head injuries, was found unconscious with broken bones, according to the FBI. The other agent, who has not been identified, also suffered severe head trauma and is in critical but stable condition.

Border Patrol union officials say that agent has no recollection of what happened.

Those officials have said they believe Martinez and the second agent were bludgeoned, possibly with rocks, in a savage desert ambush.

The area where they were found, about 50 miles north of the border, is a well-known marijuana trafficking corridor, where drug runners sometimes hide in drainage culverts to await a rendezvous with a vehicle.