PITTSBURGH -- Agents from the Attorney General's Child Predator Unit said they arrested an Allegheny County man accused of using the Internet to send sexually explicit and nude photos to what he thought was an underage girl.

Derek Lee Piovesan, 25, of Lower Burrell, was arrested Friday at his home.

Investigators said Piovesan used an online chat room to approach an undercover agent who assumed the identity of a 13-year-old girl. Agents said Piovesan told the agent that he was "Dan Snyder" from Pittsburgh.

According to the criminal complaint, Piovesan -- posing as "Snyder" -- engaged in a series of online chats with the undercover agent, which included increasingly graphic discussions about sexual activity. During the course of those online conversations, Piovesan is accused of sending the girl three photos of male genitalia.

Agents said Piovesan also requested nude pictures of the girl and instructed her to masturbate.

Piovesan faces several charges, including unlawful contact with a minor and criminal use of a communications facility.