Two whistle-blowers have accused contractors building President Trump’s border wall of smuggling armed Mexican security teams into the United States to guard construction sites, even building an illegal dirt road to speed the operation, according to court documents unsealed by a federal judge on Friday.

The two employees, who were both contracted to provide security at the sites, accused the company, Sullivan Land Services Co., or S.L.S. — as well as a subcontractor, Ultimate Concrete of El Paso — of hiring workers who were not vetted by the United States government, overcharging for construction costs and making false statements about those actions.

The whistle-blowers said Ultimate Concrete went so far as to build a dirt road to expedite illegal border crossings to sites in San Diego, using construction vehicles to block security cameras. An unnamed supervisor at the Army Corps of Engineers approved the operation, according to a complaint filed in February and released on Friday.