An Etna man faces up to 20 years in prison for running a sophisticated indoor marijuana growing facility in the Waldo County town of Frankfort.

James Mansfield, 33, pleaded guilty Thursday in U.S. District Court to conspiring to manufacture, distribute and possess with intent to distribute marijuana. Investigators seized 400 plants from the grow facility, according to a statement issued by U.S. Attorney Halsey B. Frank.

An investigation by the U.S. Drug Enforcement Administration found Mansfield conspired with others to illegally manufacture and distribute marijuana between October 2010 and August 2016, according to court records. He was not registered as a marijuana caregiver with the Department of Health and Human Services and the location of the facility was not reported to the department.

In May 2016, federal law enforcement officers executed a search warrant at the facility and recovered about 400 marijuana plants, 295 marijuana root balls and paraphernalia used to manufacture and process marijuana, according to court records.

In January, 33-year-old Nicholas Reynolds pleaded guilty to multiple charges related to his role in the marijuana operation.

Mansfield faces up to 20 years in prison, three years to life of supervised release and a $1 million fine. He will be sentenced at a later date.