Citigroup has acknowledged that last month’s high profile breach of its systems affected more than 360,000 credit card accounts, about 80 percent more than the company initially indicated.

The bank admitted just last week that a May 10 breach of its Citi Account Online system compromised approximately 1 percent of all North American card accounts, which would put the affected total at about 210,000 cards.

The updated number of compromised accounts may have been the result of the prodding of numerous state regulators, who demanded that Citigroup disclose more details about the breach, including how it occurred and what steps are being taken to mitigate its effects, according to PC World.

When asked about the updated figure, a Citigroup spokesman said that the original account total was merely an estimate, and that the company now has 23.5 million credit-card accounts in North America, not the 21 million that was originally reported, says The Wall Street Journal.

Furthermore, the number of people affected by the breach is much lower because of account closures and the fact that some customers had multiple accounts, the spokesman added.

Citigroup said in a statement that 217,657 accounts were issued new credit cards and notification letters. The company also noted that customers are not liable for any fraudulent charges and encourages card holders to review their statement to look for any discrepancies.

The financial institution also said that “data that is critical to commit fraud” was not compromised. This includes customers’ credit card expiration dates, dates of birth, security codes and social security numbers. However, Citigroup acknowledged that names, account numbers and contact information may have been compromised.

The company has implemented “enhanced procedures” to prevent a repeat occurrence of the breach, but said it could not provide further details due to the ongoing investigation.

Citigroup’s statement comes just days after the New York Times reported that the International Monetary Fund (IMF) is investigating a breach of its own.

One official told the paper that it is a “very major breach,” and that that it had been taking place over the last few months.

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Beecher Tuttle is a TechZone360 contributor. He has extensive experience writing and editing for print publications and online news websites. He has specialized in a variety of industries, including health care technology, politics and education. To read more of his articles, please visit his columnist page.

Edited by Jennifer Russell