Four executives at a Chicago area sheet-metal fabrication company were arrested on suspicion of using a staffing firm to employ at least 18 undocumented workers, the US Attorney’s Office for the Northern District of Illinois reported.

The sheet metal fabrication company, KSO MetalFab, in Streamwood, Illinois, was audited in 2017 by US Immigration and Customs Enforcement, which found 36 of the company’s 67 employees were suspected of using fraudulent work authorization documents. The company testified it fired all 36 employees. However, the US Attorney’s Office claims KSO later re-hired at least 18 of those workers by using a staffing firm.

KSO told the workers to go to the staffing agency in order to return to work, according to the office. Many of the workers used the same names they had used before the audit.

The KSO executives arrested were Dora Kuzelka, 81, of Elgin; Kenneth Kuzelka, 62, of Chicago; Kari Kuzelka, 56, of Elgin; and Keith Kuzelka, 58, of Elgin, according to the office. They are charged with one count of knowingly harboring an illegal alien and one count of knowingly engaging in a pattern or practice of hiring illegal aliens.

Keith Kuzelka left the company last year, but the other three remain in executive management positions, according to the office.

Three were arrested Friday morning while Keith Kuzelka self-surrendered to authorities Friday afternoon. All four were released on recognizance bonds.