The highest priority of any law enforcement agency is keeping citizens and communities safe from threats, including acts of terrorism or other criminal activities. When it comes to enforcing our nation's immigration laws, the U.S. Department of Homeland Security is transforming its approach by focusing our resources on those in our country illegally who have broken other criminal laws.

Accordingly, for the past two years, DHS has worked closely with our federal, state and local partners to strengthen our ability to identify and remove criminal aliens and other public safety threats under the Secure Communities program.

Secure Communities was launched in 2008. Historically, when state and local authorities booked someone for a criminal offense, they submitted fingerprints only to the Federal Bureau of Investigation. Under Secure Communities, these fingerprints are then automatically cross-checked against immigration records as well.

If the fingerprint-check indicates that an individual is in the United States unlawfully, U.S. Immigration and Customs Enforcement, a part of DHS, takes enforcement action - prioritizing the removal of individuals who present the most significant threats to public safety as determined by the severity of their crime, their criminal history and other factors.

Right now, the technology that makes this information-sharing between the FBI and the DHS possible has been activated in more than 1,200 state and local law enforcement jurisdictions in 42 states. We anticipate total activation by 2013.

To date, Secure Communities has led to the removal of more than 72,000 illegal immigrants convicted of crimes, including more than 26,000 convicted of major violent offenses like murder, rape and the sexual abuse of children. Between October 2008 and October 2010, Secure Communities resulted in a 71 percent increase in the number of convicted criminals removed from our country. A number of these cases have come from San Francisco.

Unfortunately, the facts about Secure Communities have not been communicated as clearly as they should have been, leading to confusion regarding whether state and local jurisdictions can opt out of the program and the types of illegal immigrants the program is designed to identify.

Here are the facts:

-- All illegal immigrants identified through Secure Communities have been booked into criminal custody and charged with an offense by state or local law enforcement. These arrests require probable cause that the illegal immigrant committed a state or local crime - separate and apart from violating any immigration laws.

-- Secure Communities does not authorize state or local law enforcement to act as immigration officers. The program applies to all who are arrested and booked for a crime. The fingerprints of every individual arrested and booked into custody are checked against immigration records - just as they are all already checked against FBI criminal records.

-- Secure Communities is an interoperability agreement between the DHS and the FBI; it does not require a separate agreement with a local jurisdiction. When fingerprints are provided to the FBI, they are automatically shared with DHS so that we can continue to prioritize enforcement actions against illegal immigrants who commit crimes in American communities.

As Secure Communities continues to expand, we are working closely with stakeholders at all levels to develop and implement safeguards against potential abuse. These safeguards include strengthening protections for victims of spousal abuse or other crimes; a formal complaint process for illegal immigrants who feel they have been the targets of racial profiling; an investigative process involving the DHS Office of Civil Rights and Civil Liberties and the Department of Justice; and analysis by a statistician to identify any data irregularities that could indicate misconduct in particular jurisdictions so that we can immediately initiate corrective actions. Additionally, this program will operate transparently - with information and data about Secure Communities regularly updated on the ICE website.

Secure Communities is a fair and effective means to identify illegal immigrants who should be removed from our country, and we will continue working to improve its implementation. While we continue to advocate for comprehensive immigration reform, Secure Communities is an essential tool to help us carry out our law-enforcement priorities.

Online: See video of Janet Napolitano's meeting with The Chronicle Editorial Board at sfgate.com/blogs/opinionshop