An undocumented immigrant arrested in Prince George’s County will spend 48 extra hours in jail at the request of immigration agents — regardless of the charge or the person’s past criminal record.

But the standard is different just across the line in Washington, D.C., where the city detains immigrants for extra time only if they have been involved in serious crimes.

Advocates for immigrants who are being deported under a federal program called Secure Communities are pressing to change a patchwork of local law enforcement policies across the country. The advocates say the extended detainment can heighten the chance of deportation.

In Maryland, most counties honor requests by U.S. Immigration and Customs Enforcement to hold immigrants for additional time beyond when they would ordinarily be eligible for release. That happens even though the requests are not signed by a judge. The state attorney general has concluded they are optional and local taxpayers are not reimbursed for the expense.

“There’s a huge number of people who are being locked up who would otherwise be dismissed,” said Elizabeth Alex, a lead organizer for the immigrant advocacy group CASA de Maryland.

Under Secure Communities, a high share of immigrants without criminal convictions is being deported from Maryland, according to an analysis of data by The Baltimore Sun. More than 40 percent of the Maryland immigrants deported under the program since 2009 had no prior criminal record, compared with 20 percent nationwide.

Gov. Martin O’Malley, a Democrat, wrote the U.S. Department of Homeland Security on Tuesday to ask why those deportations are taking place under a program designed to catch dangerous criminals. The department has not responded to requests for comment about the letter.

Some advocates believe part of the explanation lies in how the state handles immigration detainers.

Secure Communities provides immigration officials access to fingerprints of people who are arrested, be it for a homicide or driving without a license. The suspect’s fingerprints are sent to Homeland Security, which checks a database of people known to be in the country illegally.

If the database finds a match, federal agents ask the local jail to hold the immigrant for 48 hours beyond the time he or she would otherwise be released, so a pickup can be arranged.

What happens at that point depends on the state and sometimes the locality.

Virtually all local jails in Maryland, including the state-run Baltimore City Detention Center, agree to the requests from the federal immigration agency.

“We honor detainers,” said Terry Kokolis, superintendent at the Anne Arundel County Department of Detention Facilities. “It’s no different if it’s from Immigration or it’s from the U.S. Marshals. Both are law enforcement entities of the government.”

But across the Chesapeake Bay in Talbot County, the director of the Department of Corrections takes a different view. Douglas C. Devenyns said his agency honors the detainers in most cases — but he also believes the county has discretion.

In at least one instance — involving a mother of five children — Devenyns said, he did not further detain the inmate.

“We’ve reserved the right to determine whether or not we should necessarily honor an ICE detainer,” he said.

Unlike warrants, immigration detainers are not signed by judges and meet no standard of probable cause. The state attorney general’s office wrote in October that federal rules allow “state and local jurisdictions to exercise discretion when determining how to respond to individual detainers.”

Opponents of the practice are concerned that immigrants are being detained and deported for minor offenses. A report by the Maryland chapter of the American Civil Liberties Union in November found 76 percent of immigration detainers in Maryland between 2010 and 2012 were filed against immigrants facing traffic or misdemeanor charges.

The ACLU, CASA and others support legislation in the General Assembly that would limit the circumstances under which local jails could hold an immigrant longer than a nonimmigrant.

The TRUST Act would allow a judge to determine when an immigrant should be released.