Allegations that banks and two swaps industry groups colluded against would-be competitors in the credit-derivatives market are rippling through the investment world again.

The would-be rivals, BlueMountain Capital Management, Citadel and Pacific Investment Management Co, or Pimco, received subpoenas in recent months under an investor lawsuit alleging anticompetitive practices by the banks and industry groups, according to people familiar with the matter. No wrongdoing is alleged on the part of the firms receiving the subpoenas.