NEW YORK/WASHINGTON, Dec 18 (Reuters) – The U.S. brokerage watchdog is probing how Wall Street firms, including JP Morgan Chase and Citigroup Inc, offer stock research, two people familiar with the probe said on Friday.

The Financial Industry Regulatory Authority, which supervises nearly 4,800 brokerage firms, sent letters to more than 10 firms in early November asking for information related to their unpublished research material, one of the people said.

The same person said FINRA is eyeing the firms’ policies related to their delivery of the unpublished research material. Both sources requested anonymity because the sweep has not been made public.

The news was first reported by the Wall Street Journal, which said Morgan Stanley and Goldman Sachs are also part of FINRA’s inquiry.

FINRA is examining the firms’ meetings where unpublished research opinions were disclosed to non-research employees or clients, one source said.