(Bloomberg) -- The Federal Bureau of Investigation is seeking information on the cyberattack on London-based ION Trading UK that’s snarled global derivatives trading, according to people with knowledge of the matter.

The FBI reached out to ION executives and is reviewing how the attack is affecting customers, the people said, asking not to be identified discussing a private matter. The US agency joins UK regulators who have started their own investigations.

“The FBI is aware of this incident and has nothing additional to report at this time,” a representative of the agency said in an emailed statement. The existence of an inquiry doesn’t necessarily mean a criminal probe is under way.

A representative for ION declined to comment.

The attack affected 42 of ION’s clients and forced several European and US banks and brokers to process some derivatives trades manually. Russian ransomware gang LockBit was behind the incident, according to correspondence from ION seen by Bloomberg, the contents of which were confirmed by a company representative.  

ION told clients on Thursday that its systems won’t be fully operational until Feb. 5, and the firm still hasn’t been able to start several crucial recovery steps, according to email correspondence seen by Bloomberg.

Fallout from the hack has flowed through the futures trading industry, as transactions back up and firms struggle to determine their margin requirements to enter or exit positions. The issue is isolated to a small number of firms, and doesn’t pose a systemic risk to the financial sector, the US Treasury Department said in a statement earlier this week.

(Updates with FBI comment in third paragraph.)

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