LANSING, Mich. (AP) — Michigan says nearly 1.9 million residents may be at risk after the potential release of their Social Security numbers and names as part of a software update to the state’s unemployment benefits system.

State officials made the announcement Friday.

They say the total number of people affected will not be known until an investigation is finished. People potentially at risk include those whose payroll is processed by one of 31 third-party vendors that works with the Unemployment Insurance Agency.

The software update was done in October. The state says it identified a “vulnerability” on Jan. 30 and blocked further unauthorized access that day.

Users of the Michigan Data Automated System who potentially had access include employers and human resources professionals, not unemployment claimants or the general public.