NEW YORK (AP) — JPMorgan Chase, the nation’s biggest bank by assets, is working with law enforcement officials to investigate a possible cyberattack, said a person familiar with the situation who spoke on condition of anonymity, though the bank isn’t currently seeing any unusual fraud activity at the time.

Jamie Dimon, the bank’s CEO, said in this year’s annual report to shareholders that despite spending millions on cybersecurity, JPMorgan remained worried about the threat of attacks. By the end of this year, the bank estimates that it will be spending about $250 million annually on cybersecurity and employing 1,000 people in the area.