At least one of Wall Street's biggest banks was the target of a cyberattack reportedly launched by Russian hackers.

An official at the New York office of the Federal Bureau of Investigation told the Washington Examiner that the agency was "working with the Secret Service to determine the scope of the reported cyber financial attacks on several financial institutions."

One of the companies attacked in mid-August was the nation's largest bank, JPMorgan Chase & Co., a representative for the bank confirmed. The bank, which is not currently seeing any unusual fraud activity, is working with law enforcement to investigate the incident.

“Companies of our size unfortunately experience cyber attacks nearly every day. We have multiple layers of defense to counteract any threats and constantly monitor fraud levels,” said Trish Wexler, a spokesman for J.P. Morgan.

Bloomberg reported Wednesday that federal officials were looking into the theft of "gigabytes of data" from JPMorgan and at least one other bank by Russian hackers.

The FBI and JPMorgan declined to say whether they suspected that the attack was carried out by hackers from Russia or working on behalf of the Russian government.

The attacks came as the U.S. tightened economic sanctions on Russia as the country became increasingly aggressive in Ukraine.

JPMorgan CEO Jamie Dimon had highlighted the dangers of cyberattacks and the bank's measures to protect its customers in an April letter to shareholders. The bank planned to spend $250 million on cyber security efforts involving 1,000 workers in 2014, according to Dimon.

Treasury Secretary Jack Lew highlighted the potential danger of cyberattacks at a conference in July, warning that "cyberattacks on our financial system represent a real threat to our economic and national security."

The Senate Intelligence Committee passed a cybersecurity bill in July. The legislation, which would grant companies immunity for sharing certain kinds of information with law enforcement, is controversial among privacy advocates.