WASHINGTON  The nation’s top immigration enforcement official ordered the destruction of photographs of an office Halloween party that showed a white agency employee dressed as a black detainee, according to a Congressional investigation whose report was released on Tuesday.

The Democratic staff of the House Committee on Homeland Security said Julie L. Myers, the assistant secretary of homeland security for immigration and customs enforcement, ordered that the photos be removed from a digital camera in a “coordinated effort to conceal” her role in awarding one of the top costume prizes to the employee.

The report said Ms. Myers, who was acting assistant secretary at the time, might have moved to cover up the events to avoid derailing her Senate confirmation.

The Congressional committee provided no evidence of an intentional cover-up.

Kelly A. Nantel, an agency spokeswoman, confirmed Tuesday that Ms. Myers had ordered that the photographs be deleted, but said she had done so because she belatedly realized that the costume was inappropriate and that it would be offensive if the photos were included in any agency publications.