Lawmaker seeks source of information on Obama's aunt

WASHINGTON (CNN) - A Democratic lawmaker on Saturday asked Homeland Security Secretary Michael Chertoff to investigate a leak to reporters regarding the immigration status of Democratic presidential candidate Barack Obama's aunt, suggesting the Bush administration may have been behind it.

"I was startled to read in today's Associated Press that a 'federal law enforcement official' has leaked information about an immigration case involving a relative of Senator Obama," said a letter sent to Chertoff by Rep. John Conyers, D-Michigan, who chairs the House Judiciary Committee.

The AP reported Saturday that Obama's Kenyan aunt, Zeituni Onyango, is living in the United States illegally, even though an immigration judge rejected her request for asylum four years ago. The story cites two sources, one of them a federal law enforcement official.