MINNEAPOLIS (AP) — The union representing workers at a janitorial company operating in the Twin Cities say half its workers are being fired because they failed to provide documents that show they’re in the United States legally.

Service Employees International Union Local 26 says 240 employees at Harvard Maintenance are being dismissed through the end of the month. One worker tells Minnesota Public Radio News that Harvard Maintenance sent a letter in December saying she had 90 days to produce proper documentation after the U.S. Department of Homeland Security notified the company it suspected some of its workers were illegal immigrants.

Two years ago, more than 1,200 janitors at ABM, another large commercial cleaning company, lost their jobs after a similar immigration audit. Harvard Maintenance did not immediately return a call seeking comment.