"Impersonation and deception are illegal under New York law," said Eric Schneiderman.
The company, Devumi, stands accused of stealing real people's identities, which it denies, according to the New York Times.
The paper linked the "follower factory" to a host of celebrity accounts.
The New York Times published an in-depth report on Devumi on Saturday, including interviews with people who alleged their account details and profile pictures had been copied to create realistic "bots".
It is alleged that others who wanted to increase their follower count, including actors, entrepreneurs and political commentators, could then pay to be followed by the bots.
On social media, high follower accounts boost influence, which can impact public opinion, or bring advantages, such as job offers or sponsorship deals, to account holders.
Mr Schneiderman said he was concerned that such "opaque" operations were undermining democracy.