ISLE OF PALMS, S.C. (AP) -- Gov. Nikki Haley said Thursday that an investigation into the hacking of millions of state tax returns is almost complete and she hopes to report to South Carolinians next week on what happened.
She also said it's unclear whether as many as 3.8 million returns were compromised by a hacker with an international IP address who got into the state Revenue Department system.
Haley, speaking to reporters following remarks to the state Chamber of Commerce, said the forensic investigation was about 95 percent complete.
"Everything we are being told now is that there is nothing that could have been done that would have prevented this," she said. "I am not prepared to tell you that because as long as 5 percent is out, we don't know the whole story."
The governor added: "I want to make sure the whole story is told. I want to make sure I know what happened, how it happened, if there was anything that could have been done.
Officials announced last month the security breach compromised both Social Security numbers and tens of thousands of credit card numbers. They have said as many as 3.6 million tax returns dating back to 1998 may have been compromised.
Haley said Thursday that number may be high, but out of an abundance of caution, officials wanted all taxpayers who filed during that period to sign up for credit monitoring.
"That's us being overly cautious. That is not saying someone got a hold of everything from 1998 forward. That's me saying I want to make sure we have everybody covered," Haley said.
The Haley administration has been criticized by some state lawmakers for not letting the public know more quickly that the tax returns had been hacked.
State Law Enforcement Division Chief Mark Keel said at a news conference last month that state officials were made aware of the problem by the Secret Service on Oct. 10 and that the hacker may have gotten into the files, stored in a computer in Columbia, as early as late August. State officials waited 16 days after they learned of the breech to make it public.
"Chief Keel has made it very clear that the waiting was based on what the Secret Service told us and what he told us and the situation would have been a lot worse if we had not let them do their jobs," the governor said on Thursday.
Officials have said that the delay was so investigators could reach certain benchmarks in their probe into the hacking.
A top cyber security told the AP earlier that stolen credit card information like that from the hacked South Carolina tax returns is quickly sold on the Internet black market and chances of finding whoever did it are slim.
Michael DuBose, former chief of the U.S. Justice Department's computer crime section who now works for the international cyber security company Kroll, said Social Security numbers are sold in the same way.