Updated

Immigration officials ordered local law enforcement officials to detain more than 800 U.S. citizens in jail or police custody until they could review their immigration paperwork, according to an analysis of government data.

The detentions – generally an illegal practice – occurred between 2008 and 2012, according to an analysis by the Transactional Records Access Clearinghouse, a research organization affiliated with Syracuse University.

Immigration and Customs Enforcement, or ICE, also ordered the detention of 28,489 legal permanent residents, the vast majority of whom had no criminal conviction, the analysis said.

Those detainers – which are ICE notices sent to local law enforcement agencies, including jails, when the immigration agency intends to arrest a person – were among almost 1 million that ICE issued in a 50-month period.

“While the press quoted ICE officials as contending that the agency did not track how many U.S. citizens had been inadvertently held in immigration detention, the data released. . .indicates that a substantial number of U.S. citizens may be affected,” the TRAC report said. “It is illegal for [ICE] to detain U.S. citizens, and to do so is a significant violation of their constitutional rights.”

Groups that advocate for immigrant rights said that the findings underscore what they say is the problematic partnership between ICE and local law enforcement. They also said it raises more doubts about the Obama administration’s vows to focus immigration resources on removing the most dangerous criminals.

"This is further proof of the troubling contradiction between the president's words and his actions on immigration,” said Pablo Alvarado, executive director of the National Day Laborer Organizing Network, in a statement. "The Obama administration's policy of using police as immigration 'force multipliers'. . . has violated civil rights, imperiled public safety, and compounded injustice."

ICE did not return a call seeking a comment about the report.

The Los Angeles Times quoted an ICE spokeswoman as saying that TRAC’s findings looked at data from a period before new standards took effect in December.

“This guidance limits the use of detainers to individuals who meet the agency’s enforcement priorities and restricts the use of detainers against individuals arrested for minor misdemeanor offenses such as traffic offenses and other petty crimes, helping to ensure that available resources are focused on apprehending convicted felons, repeat offenders and other ICE priorities,” the newspaper quoted an ICE statement as saying.

TRAC reported that more than 3,500 local, state and federal agencies received at least one ICE detainer between fiscal year 2008 and the start of fiscal year 2012. (Fiscal years run from October of one year to September of the following year.)

Most of the detainers, the analysis found, involved people who did not have criminal convictions.

Slightly less than 9 percent of the people targeted for detainers were “Level 1,” or “serious” offenders, TRAC said. But the report said ICE’s criteria for classifying someone as “Level 1” appeared flawed.

“Their records show that all too often the most serious Level 1 offenders have only been convicted of traffic violations and immigration violations (illegal entry) rather than some more serious offense,” the report said.