The Department of Homeland Security is systematically reviewing thousands of pending immigration cases and moving to dismiss those filed against suspected illegal immigrants who have no serious criminal records, according to several sources familiar with the efforts.

Culling the immigration court system dockets of noncriminals started in earnest in Houston about a month ago and has stunned local immigration attorneys, who have reported coming to court anticipating clients' deportations only to learn that the government was dismissing their cases.

Richard Rocha, an Immigration and Customs Enforcement spokesman, said Tuesday that the review is part of the agency's broader, nationwide strategy to prioritize the deportations of illegal immigrants who pose a threat to national security and public safety. Rocha declined to provide further details.

Critics assailed the plan as another sign that the Obama administration is trying to create a kind of backdoor "amnesty" program.

Raed Gonzalez, an immigration attorney who was briefed on the effort by Homeland Security's deputy chief counsel in Houston, said DHS confirmed that it's reviewing cases nationwide, though not yet to the pace of the local office. He said the others are expected to follow suit soon.