If they truely are "employees", then you are required to issue them a W-2 regardless of what you paid them during the tax year. If they are not employees then you would need to issue them a 1099-MISC only if you paid any one individual more than $600 during the tax year. In order for you to meet that legal requirement, you need to have either their SSN or their ITIN. If they don't have an SSN or ITIN, then most likely they are not allowed to work legally in the U.S. But if they can work here legally and are U.S. Citizens or hold resident alien status, they need to get an SSN yesterday if not sooner. If they are non-resident aliens they need to obtain an ITIN from the IRS by filing form W-7 with the IRS.
The law requires anyone working in the U.S. to have an SSN, or an ITIN if they do not qualify for an SSN. If you are caught employing someone not authorized to work here, the excuse of "I didn't know" wont cut it. You're looking at fines that could be hefty enough to bankrupt you, and the IRS *will* *not* *care*.
Please seek legal advice on this to protect your business as well as yourself and personal assets.