The Washington State Department of Licensing said the personal information of potentially millions of licensed professionals may have been exposed after it detected suspicious activity on its online licensing system.

The agency licenses about 40 categories of businesses and professionals, from notaries to real estate agents, and it shut down its online platform temporarily after learning of the activity in January, agency spokesperson Christine Anthony said Friday. Data stored on the system, which is called POLARIS, could include Social Security numbers, birth dates and driver’s license numbers.

The agency doesn’t yet know whether such data was actually accessed or how many individuals may have been affected, Anthony said.

Anthony said the agency has been working with the state Office of Cybersecurity, the state Attorney General’s Office and a third-party cybersecurity firm to understand the scope of the incident, The Seattle Times reported Friday.

In the meantime, the shutdown of the POLARIS system is causing problems for some professionals and firms that need to apply for, renew or modify their licensing.

The disruption comes at a busy time for real estate agents, appraisers and home inspectors as the state’s real estate market begins to pick up after its typical winter slowdown.

The size of the breach remains unclear. Data from 23 professions and business types licensed by the state is processed via POLARIS, Anthony said.

Within those 23 categories, which also include bail bonds agents, funeral directors, home inspectors and notaries, the agency has around 257,000 active licenses in its system, Anthony said, adding that “there are likely more records that may be identified while conducting our investigation.”