LOS ANGELES – Lawyers for JPMorgan Chase & Co. are asking financial news and data company Bloomberg LP to turn over any records it has of reporters looking up the log-in and usage data of JPMorgan employees.

A formal letter was sent this week, a person familiar with the matter said. The person wasn’t authorized to speak publicly and spoke on condition of anonymity.

The letter seeks data going back to 2008 as the bank examines whether the seller of ubiquitous trading-data terminals was in breach of contract, the person said.

It comes after the revelation Friday that, until recently, Bloomberg reporters had special access to client usage data and sought to use it to break stories. On Monday, Bloomberg News Editor-in-Chief Matthew Winkler apologized for the practice, which he said had been going on since the 1990s. He said the special access for reporters had been cut off last month after Goldman Sachs complained.

A Bloomberg spokeswoman declined comment Wednesday.

JPMorgan’s letter sought confirmation that inappropriate access by reporters had stopped; a description of the controls in place to prevent a recurrence; and logs of all Bloomberg staff and a description of their roles and what they were checking, the person said.

Bloomberg has acknowledged that reporters could see when specific clients had last logged in, their most frequently used commands on the terminal, and could even access transcripts of help-desk inquiries by users. But it said reporters weren’t able to glean whether users looked at specific stocks or bonds and could not access their messages.

The Federal Reserve is also looking into whether Bloomberg journalists tracked data about terminal usage by top Fed officials.

Investment banks like JPMorgan and Goldman have chafed at the high price of Bloomberg terminals — which cost $20,000 a year — and what they view as its growing incursion into their business.

Since 1996, Bloomberg has operated a division called Bloomberg Tradebook that acts as a broker dealer, facilitating the trade of equities in the U.S. The company is also applying to the government to be certified to facilitate trades of complex derivatives like credit default swaps.