FILE PHOTO: A woman passes by a JPMorgan Chase bank in Times Square in New York City, U.S., March 7, 2019. REUTERS/Brendan McDermid/File Photo

(Reuters) - JPMorgan Chase & Co, the largest U.S. bank, has taken action against more than a dozen traders for using WhatsApp at work, firing one and cutting bonuses for the rest, Bloomberg news reported on Wednesday, citing people with knowledge of the matter.

Senior credit trader Edward Koo was formally dismissed for breaking rules by creating a WhatsApp group and using it to discuss market chatter with other trading employees, according to the report.

Koo was placed on leave in January while the bank reviewed whether he breached its policies by using WhatsApp group chats with colleagues, Bloomberg news had reported then.