In an unusual move, a group of illegal immigrants arrested in a work-site raid at a Bellingham engine plant last month has been released from detention, without bond, and given permission to work legally, while a post-raid investigation continues.

Agents with U.S. Immigration and Customs Enforcement had arrested 28 workers during a Feb. 24 raid at Yamato Engine Specialists. ICE investigators said many of the workers from Mexico and Central America had used false documents to obtain employment at the plant.

Saying she had not been made aware of the raid, Secretary of Homeland Security Janet Napolitano immediately ordered a probe into the actions of the Seattle-based ICE team that conducted the raid. Napolitano and the Obama administration have said they want to shift the focus of these raids from the illegal workers themselves to the employers who knowingly hire them.

Immediately following the arrest of the workers, three women with children were released on humanitarian grounds and a fourth worker with a medical condition was also allowed to leave.

Last week, all the remaining workers not deported were allowed to leave the Northwest Detention Center in Tacoma without bond — a move immigration attorneys call highly unusual.

Illegal immigrants arrested in raids or other ICE actions are often detained for months until they can get a hearing before a judge. Sometimes they waive their rights to a hearing and agree to return home.