Also under scrutiny is whether a major security firm was "illegally smuggling weapons into Iraq," according to a letter to IG Howard J. Krongard that was obtained Tuesday by The Associated Press.

The investigation involves allegations that "your strong affinity with State Department leadership and your partisan political ties have led you to halt investigations, censor reports, and refuse to cooperate with law enforcement agencies," Krongard was told.

Based on allegations made by a number of current and former senior investigators who worked for Krongard, the letter from the House Oversight and Government Reform Committee also questioned whether he adequately investigated illegal labor trafficking allegations involving the Kuwaiti company that was building the Baghdad embassy.

Krongard, in testimony before the committee in July, dismissed allegations that foreign workers were mistreated in building the new complex in Baghdad. But he acknowledged that some recruiters may have misled foreign workers about pay expectations and living conditions.