Citigroup on Thursday revised its third-quarter earnings downward by $600 million, citing an unexpected spike in legal costs.

The bank two weeks ago reported a profit of $3.4 billion. With the addition of the legal costs, it says that its quarterly profit was $2.8 billion.

"The increase resulted from rapidly-evolving regulatory inquiries and investigations, including very recent communications with certain regulatory agencies," the bank said in a press release.

No additional details were provided for the adjustment.

Citi has been weighed down by legal bills in recent months. The bank in July agreed to pay $7 billion to settle a government probe into mortgage-backed bonds. Its Mexican bank, Banamex, was also recently fined $2.2 million by regulators over charges of fraud.

Citi was also one of 16 banks sued by the Federal Deposit Insurance Corp. over manipulations to the London interbank offered rate.

Regulators have also begun exploring whether to revisit — and possibly strengthen — earlier legal settlements with some of the nation's biggest banks, the New York Times reported Wednesday.

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