New York Attorney General Eric Schneiderman's office is investigating the posting of false bids and offers in the foreign exchange options market for emerging market currencies, a person familiar with the matter said on Monday.

The person, who spoke on condition of anonymity, said subpoenas were issued last week to four brokerages: BGC Partners , GFI Group, TFS-ICAP and Tullett Prebon Financial Services.

U.S. authorities have increased their scrutiny of so-called 'ghosting' or 'spoofing,' in which a trader tries to create a false appearance of market interest in a stock, commodity or other asset by placing orders and then immediately canceling them.

Representatives of BGC, ICAP and Tullett Prebon declined to comment. GFI is majority-owned by BGC.

Shares of each of the publicly traded companies were trading lower on Monday, in a broadly flat market.