A CNN investigation released this week found the U.S. Border Patrol has been haphazard about tracking and recording deaths of migrants who cross into the United States illegally.

Tracking these deaths has been part of the agency’s mission for 20 years, but the report found nearly 600 uncounted deaths over the years by reviewing records, databases from other agencies in border states and conducting interviews. There are indications the undercount could be much higher.

CNN reported Arizona has the biggest gap between migrant deaths reported by the border patrol and the uncounted deaths with more than 400 tallies that were not included in the Border Patrol’s reporting over the past 16 years. We know this because of the agencies in Arizona that have worked on putting together their own count led by the Pima County Medical Examiner’s Office.

The Show spoke with Greg Hess, the chief medical examiner for Pima County.