Most of the Customs and Border Protection Agency's (CBP) bad apples come from posts along the Southwest border, according to a recent investigation.

“Data indicate that the overwhelming majority of CBP employees adhere to the agency’s integrity standards; however, a small minority have been convicted of engaging in corruption due, in part, to the increasing pressure fromdrug-traffickingand other transnational criminal organizations … particularly along the southwest U.S. border,” according to a GAO report released on Thursday.

A GAO investigation found that 65 percent of arrests among CBP employees for misconduct or corruption were of CBP officers (CBPOs) and Border Patrol Agents (BPAs) stationed along the United States’ border with Mexico.

The charges range from non-mission related conduct like DUIs and domestic violence to “mission compromising corruption” like smuggling drug and selling counterfeit documents.

CBP is the largest uniformed law enforcement agency in the United States. More than 21,000 BPAs 20,000 CBPOs patrol air land and seaports nationwide. On the U.S. southwest border, there are about 5,500 CBPOs and 18,000 BPAs.

Their misconduct accounts for less than once percent of the total workforce, but CBP officials told the GAO that they worry that a few bad apples could have an impact on the integrity of the agency as a whole.

Last February a separate Inspector General investigation found that CBP employed people with criminal records for drug smuggling, human trafficking, and attempted murder because of inadequate background checks.

Based on analysis of data from 2005 to 20012, the GAO found that 144 employees were arrested or indicted for corruption. More than 2,100 were involved in incidents of misconduct.

During the same period of time, CBP saw a hiring surge.

Thefull report includes a response from the Department of Homeland security and GAO’s recommendations for improving the hiring process, includingpolygraph testing, and compiling corruption data.