SAN DIEGO -- Two Border Patrol supervisors, who released illegal immigrants from custody in exchange for more than $186,000 from smugglers, pleaded guilty Friday to bribery and filing false tax returns.

Mario Alvarez, 45, and Samuel McClaren, 44, each face up to 18 years in federal prison when they are sentenced Sept. 29 by U.S. District Judge John Houston.

Alvarez and McClaren, both from Imperial, were indicted March 9 and charged with conspiracy to smuggle aliens for financial gain, conspiracy to commit bribery, bribery, making a false statement, smuggling aliens for financial gain, filing a false tax return and criminal forfeiture.

"These are Border Patrol agents who smuggled illegal aliens. It doesn't get much worse than that," said U.S. Attorney Carol Lam.

McClaren told the judge Friday that between June 2003 and March of this year, he took $85,940 from a smuggling organization in exchange for failing to enforce immigration laws, specifically by releasing illegal immigrants from federal custody.

According to the indictment, the defendants worked in the Mexican Liaison Unit in El Centro and were assigned to administer the Guide Identification Prosecution Program, a joint effort by the United States and Mexico to catch and prosecute immigrant smugglers.

Under GIPP, smugglers who are not prosecuted in the United States are to be deported and prosecuted by Mexican authorities.

Each defendant told the judge that they took bribes to get illegal immigrants -- and immigrant smugglers -- released from the custody of the Department of Homeland Security.

McClaren also admitted that he underreported his income on his 2004 federal tax return, causing a loss to the U.S. government of $8,667.

Alvarez told the judge that he took $100,300 in bribes from the smuggling organization over the same time period.

Alvarez also admitted underreporting his income on his 2004 federal tax return, causing a loss to the U.S. government of $21,221.

Both defendants -- who were suspended without pay after being arrested and have since left the Border Patrol -- agreed to criminally forfeit their portion of the $186,240 in illicit proceeds.