About nine other banks and brokerages were infiltrated by the same group of hackers who recently attacked computer systems at JPMorgan Chase & Co, the New York Times reported late on Friday, citing unnamed people briefed on the matter.

The report, which could not be independently verified and did not identify any of the victims beyond JPMorgan, said it was not clear how serious the attacks had been.

JPMorgan said on Thursday that names and contact information for some 83 million household and small business customers were stolen, making it one of the biggest data breaches in history.

The New York Times said the breadth of the attacks and uncertainty about the motives of the hackers are troubling U.S. policymakers and intelligence officials.

Representatives with the U.S. Secret Service could not be reached for comment on Saturday morning. The Secret Service is investigating the attack on JPMorgan.