A Ponchatoula man received a 27-year prison sentence Wednesday for downloading more than half a million images of child pornography — one of the largest collections found in the state, the U.S. Attorney’s Office said.

Robert Swan, 53, was sentenced to serve 327 months in prison, followed by supervised release for life, for his role in sexually exploiting children as young as 4 weeks old, U.S. Attorney Kenneth Polite said in a news release.

Swan also must register as a sex offender and pay a $100 special assessment fee.

Investigators with the state Attorney General’s Office’s Cyber Crimes Unit seized 15 digital devices, including computers and flash drives, from Swan’s home in January 2013, after determining he had distributed sexually explicit videos of children between the ages of 2 and 10 on a peer-to-peer program.

Between May 2010 and January 2013, Swan had cataloged more than 500,000 images and videos depicting children being forced to engage in sexually explicit conduct, Polite said in the news release.

Agents also found evidence that, around January 2010, Swan and another man, Thomas Middleton, had forced a then-3-year-old girl to engage in sexually explicit conduct while Swan recorded it. Middleton was convicted in the Western District of Kentucky for his role in that offense, Polite said.

Swan’s prior conviction in 1987 for lewd and lascivious assault of a minor in Escambia County, Florida, caused him to face an enhanced sentence in this case, Polite said.