SOLEBURY TOWNSHIP, Pa. (CBSNewYork/CBS Philly/AP) — Four young men went missing in suburban Philadelphia last week, and now authorities in Bucks County, Pennsylvania have named a person of interest in connection to their disappearance.

A busload of police cadets was brought in Tuesday to help search a large farm for the missing men, believed to be victims of foul play, as a prosecutor described a man held on an unrelated gun charge as a person of interest in the investigation.

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A post on the Bucks County District Attorney’s Twitter feed Tuesday night says 20-year-old Cosmo DiNardo had been released after posting 10 percent of his $1 million bail in cash.

DiNardo, whose family owns the sprawling farm property that has become the center of the search for the missing men, was arrested on Monday for illegally possessing a 20-gauge shotgun and ammunition.

But Weintraub did not call him a suspect, and cautioned there is often a “chasm” between being called a “person of interest” in an investigation and being charged with a crime.

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A court affidavit said DiNardo had a history of mental illness and had been involuntarily committed to an institution for inpatient care. It did not say when the commitment had occurred. The charge had been dismissed by a judge in February but was refiled.

Numerous law enforcement agencies were taking part in the third day of the search of farmland in Solebury Township, about 30 miles north of Philadelphia. The missing are 22-year-old Mark Sturgis, 21-year-old Tom Meo, 19-year-old Dean Finocchiaro, and 19-year-old Jimi Tar Patrick, a student at Loyola University in Baltimore.

Four young men went missing last week in Bucks County, Pennsylvania. Authorities named a person of interest Tuesday. (credit: KYW)

Patrick disappeared on Wednesday, the other three on Friday.

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“We are going through it with the equivalent of a fine-tooth comb,” Weintraub said of the 90-acre property where authorities have centered their investigation.

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Authorities also searched a property in Bensalem that the DiNardo family owns, CBS Philly reported.

DiNardo’s lawyer and parents could not be reached for comment.

Weintraub said it remains unclear what relationship the missing men have with each other as he urged the public to disclose any relevant information. Sturgis’ father has said that his son and Meo are longtime friends who work in construction for him. He said Finocchiaro is a mutual friend of theirs.

The FBI, Pennsylvania state police and five local law enforcement agencies have joined the case, Weintraub said.

Cadaver dogs and heavy equipment were brought in Tuesday afternoon to aid in the search for the missing men.

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(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)