Mollie Tibbetts' alleged killer passed the government's background check for migrant workers, his employer says as he is charged with murder

The Iowa farm which hired Christhian Rivera, 24, insisted that the illegal immigrant had passed the government's own vetting system for migrant workers before they employed him.

Rivera, who has been living in the US illegally for the last 4 to 7 years, followed missing University of Iowa student, Mollie Tibbetts, in his car as she jogged and tried to have a conversation with her on July 18 but when she threatened to call the police, he attacked her in Brooklyn, Iowa.

Rivera led police to Mollie's body which he'd hidden in a corn field and was on Tuesday charged with first-degree murder in Tibbett's death. 

Yarrabee Farms, where the Mexican national had worked for the past four years, said his status had been checked with the Department of Homeland Security's E-Verify website - a site which allows employers to establish the eligibility of employees, both US or foreign.