From this:

An anonymous tip triggered an investigation of undocumented workers at Camp Lejeune, resulting in 40 people being detained and a federal investigation, a base spokesman said.

Camp Lejeune officials detained 27 people at base gates during security checks Wednesday and another 12 at various construction sites Monday...

Details on where the workers are from, how they got on base and what will happen to them now were not immediately made available...

...Immigration and Customs Enforcement is not commenting now because the investigation is ongoing. Carpenter declined to mention any contractors by name, saying only that investigators were "looking into the practices of several contractors right now..."

Previously in this long line of stories about illegal aliens working at military installations: "Arresting illegal aliens at Air Force base puts New York Times in tizzy".