JPMorgan Chase disclosed this week that less than 5 percent of its nearly 3,700 financial advisers are black and said it still had work to do to improve diversity in its ranks. But some Democratic lawmakers want to know more.

Congressional Democrats in both chambers were critical of the bank on Thursday for its response to questions they raised in response to a New York Times report about racism at some of the bank’s branches in Arizona.

A financial adviser there recorded his boss disparaging a black customer as being “from Section 8,” a reference to public housing, and saying she did not deserve to be in the bank’s program for elite customers. Another black customer, the former National Football League player Jimmy Kennedy, struggled for months to get access to a package of perks for wealthy clients — a delay that an employee told him was connected to his race.

Last month, five Democratic senators and two Democratic congressmen sent letters to JPMorgan’s chief executive, Jamie Dimon, seeking a detailed explanation of those episodes and an accounting of the bank’s plans to address black employees’ discrimination complaints.