New York Attorney General Eric Schneiderman’s office is questioning a pharmaceutical company criticized last month for sharply increasing the price of treatment for a deadly parasitic infection.

Schneiderman’s anti-trust bureau wrote Monday to Turing Pharmaceuticals CEO Martin Shkreli seeking a response to concerns that the company may be “unlawfully” restraining competition by distributing the drug Daraprim only through a limited number of specialty pharmacies in order to prevent generic manufacturers from obtaining access to samples.

The letter says the New York City-based company’s actions could “impede access” to a critically important drug.

Turing said last month that it would reduce prices for Daraprim, used to treat toxoplasmosis, after facing criticism for hiking the price in August from $13.50 per pill to $750.

Messages left with Turing were not initially returned.