On December 10, 2008, U.S. Immigration and Customs Enforcement (ICE) agents announced the arrest of 15 undocumented workers in Whiting, Indiana. The undocumented workers were employed as contract janitorial workers at a BP Whiting oil refinery. ICE initiated the investigation after receiving information that undocumented workers were being contracted by an Illinois company to work at the BP refinery, and they had access to secure areas of the plant. Because ICE has identified oil refineries as critical infrastructure facilities, crucial to our nation's ability to function and vulnerable to attack, ICE scrutinizes the employment of any worker employed at oil refineries very carefully. The undocumented workers, 14 Mexican nationals and 1 Guatemalan national, were employees of United Building Maintenance, a Carol Stream, Illinois janitorial services provider. The undocumented workers performed janitorial services at the BP refinery.