The Obama administration will not release the results of an investigation into why an illegal immigrant with two drunk driving convictions went almost two years without a deportation hearing before a crash that killed a Virginia nun, a senior official said.

Carlos Martinelly-Montano, 23, who entered the country illegally from Bolivia as a child, is accused of killing Sister Denise Mosier, 66, and injuring two other Benedictine nuns while driving drunk in Prince William County on Aug. 1.

The furor over the way Martinelly-Montano's case was handled by Immigration and Customs Enforcement prompted the agency's boss, Department of Homeland Security Secretary Janet Napolitano, to announce an investigation.

"Why is it that this individual was driving?" Napolitano asked at a news conference Aug. 2, one day after the accident on Bristow Road. "He was in the removal process. Why did the removal process take so long?"

The inquiry is complete, but Homeland Security does not plan to make the results public, according to the senior official, who spoke on condition of anonymity because he was not authorized to speak about the matter.

"It's a document that includes law enforcement sensitivities, so it will not be made public," the official said. He declined to discuss the nature of those sensitivities.

In response to questions about the investigation's conclusions, DHS spokesman Matt Chandler issued an e-mailed statement that said: "The Secretary's Office has received the review of the circumstances by which the individual was released in 2008 and are in the process of looking over the findings. Due to the ongoing criminal matter at hand, it would be inappropriate to comment further."

Told of the government's decision to withhold the investigation's results, Corey Stewart, chairman of the Prince William County Board of Supervisors, expressed outrage.

"Prince William County has never been more frustrated with the Department of Homeland Security and Secretary Napolitano than it is right now," said Stewart, who has been demanding, without success, that ICE detail how many illegal immigrants are being released into the community after they've been charged with crimes. "They say one thing and do another. They say they are going to do something and then backtrack."

After Martinelly-Montano's second drunken driving arrest in October 2008, ICE officials released him on his own recognizance while he was awaiting a deportation hearing. He was in regular touch with immigration officials, even as his hearing was delayed three times.

Martinelly-Montano lost control of his Subaru at 8 a.m. Sunday, Aug. 1, and collided head-on with the car bearing the nuns, who were on their way to a retreat at their Bristow monastery. In addition to Mosier's death, the two nuns with her were critically injured.

Sister Charlotte Lange, 70, who was driving, is still hospitalized at a rehabilitation facility in Richmond but is expected to make a full recovery, according to Sister Cecilia Dwyer, prioress of the Benedictine Sisters.