Insurance giant Anthem Inc. said Thursday that hackers had access to customer data going back to 2004 as investigations continue into the massive breach.

The nation’s second-largest health insurer disclosed the new time frame as it prepares to offer two years of free identity-theft protection to millions of affected consumers starting Friday.

Anthem announced last week that hackers infiltrated one of its giant databases containing Social Security numbers, birth dates, addresses and other personal information of up to 80 million Americans.

The Indianapolis-based company said its internal investigation was ongoing and it hadn’t yet determined which customers might have been affected.

In the meantime, Anthem said all current and former customers going back to 2004 can begin enrolling Friday for two years of identity theft protection and free credit monitoring.

Consumers can sign up and learn more details online or by calling (877) 263-7995.

Anthem initially proposed one year of identity theft protection in some states, but regulators pushed for a longer period given the severity and scope of the data breach.

“Our goal is to provide peace of mind to consumers, while minimizing frustration,” the company said in a statement. “Consumers will be able to sign up for these services, which will be offered free of charge for two years, beginning Friday.”

Anthem faces multiple government investigations by the FBI, federal health care officials and state insurance commissioners.

“We appreciate the identity-protection services being put into place by Anthem, but reviewing the scope and implications of this event will be a long process,” said Monica J. Lindeen, Montana’s commissioner of securities and insurance and president of the National Association of Insurance Commissioners.

Lindeen said state regulators were meeting with Anthem executives on a daily basis.

Anthem has more than 37 million customers in California and 13 other states.

But the company warned last week that the database that was breached also had information on other Blue Cross Blue Shield patients from all 50 states who had sought care in Anthem’s coverage area.