COLUMBIA (WACH/AP) -- Gov. Nikki Haley is holding a news conference to update South Carolinians on the massive security breach at the state's tax collection agency.

Haley will speak to reporters Tuesday afternoon at the Statehouse.

The governor said last week she would soon release results of Mandiant's investigation of the cyber-attack. The Department of Revenue hired the Virginia-based computer security firm last month after learning that millions of tax returns were accessed from an agency server.

The number of affected taxpayers has grown to 3.8 million individual filers and up to 657,000 businesses.

Officials say Mandiant's recommendations and equipment closed the security gap Oct. 20. They hope Mandiant determines exactly what information was taken.

Until then, they say anyone who's filed a return since 1998 should assume everything on it was accessed.