(CNN) There was no evidence a crime was committed when a US Border Patrol agent was killed more than two months ago while on patrol in West Texas, according to a new government memo obtained by CNN.

The internal memo from Carla L. Provost, acting chief of US Border Patrol, is the third indication that there appears to be no evidence of foul play that led to the mysterious death of US Border Agent Rogelio "Roger" Martinez, who was found critically injured near a concrete-lined culvert along with his partner.

Provost's February 8 memo, which was sent to Border Patrol employees, including the rank-and-file agents, lays out the findings of the FBI's investigation up to this point. It also echoes an earlier memo from Kevin McAleenan, acting commissioner of the US Customs and Border Protection, which oversees the border patrol.

US Border Patrol agent Rogelio "Roger" Martinez

"Currently there is no evidence indicating the presence of other persons or the commission of a crime," Provost's memo said.

"Unfortunately, the investigation up to this point has not revealed exactly what took place prior to the two [border patrol agents] being injured and what might have caused BPA Martinez to fall into the culvert," Provost's memo said.

Read More