The company, Howard Industries, was the target of the largest immigration raid at a single location in U.S. history — despite using E-Verify for new hires, as mandated by state law.

How could so many undocumented workers have been hired? One big explanation could be the timing. The investigation started two years ago, before the company was using E-Verify.

Also to blame might be the fact that E-Verify doesn’t do much to prevent identity theft. If an undocumented employee uses another person’s name and social security number, the system won’t tell employers that — it only matches names and SSNs.

E-Verify is set to expire in November, unless Congress approves an extension. The House of Representatives passed a bill to extend the program for five more years, but the Senate has yet to take action.

Experts say situations like Howard’s are likely to up the ante in the debate on whether to scrap it, keep it as a voluntary or make it mandatory for employers. We’ll keep you posted.