Inside the mysterious disappearances of 4 young men

— -- The search for four young men who have been mysteriously missing for days "is a marathon not a sprint," a southeast Pennsylvania prosecutor said today.

Bucks County District Attorney Matthew Weintraub said today that no human remains have been recovered in the search for the missing men; however, authorities are combing through a property in Bucks County, which is about 40 miles northeast of Philadelphia.

Here is what we know about the disappearances:

4 young men vanish

Nineteen-year-old Jimi Tar Patrick has been missing since Wednesday, while 22-year-old Mark Sturgis, 19-year-old Dean Finocchiaro and 21-year-old Tom Meo all disappeared Friday.

While Weintraub said the relationship between the men is not clear, Sturgis' father "has said that his son and Meo are longtime friends who work in construction for him" and that "Finocchiaro is a mutual friend of theirs," The Associated Press reported.

Authorities fear the men may have been victims of foul play.

A person of interest

Cosmo DiNardo, 20, who was taken into custody on Monday on a charge stemming from February of illegally possessing a shotgun and ammunition, was named today as a person of interest in the men's disappearances, as investigators continue searching a property that belongs to the DiNardo family.

Weintraub stressed today that while Dinardo is a person of interest, "Sometimes the chasm between being a person of interest and being a person that’s actually accused or arrested and certainly convicted of a crime is so wide that we never cross it. ... Dinardo has been arrested on charges that do not relate or pertain to this case.

"We will continue our investigation," Weintraub added. "Mr. Dinardo may or may not be included."

DiNardo was being held on $1 million bail because he is considered a flight risk, Weintraub said. The Bucks County District Attorney's Office announced Tuesday afternoon that he was released on bail, 10 percent of which was paid in cash.

The search

Weintraub said that searchers have been combing all of Bucks County in connection to this case, though the main site being searched is property owned by the DiNardo family. Sources told ABC News a cellphone ping is what led authorities the property, though Weintraub said he could not say what directed officials there.

"We are still gradually sifting through the property," Weintraub said. "It’s 90-some acres and we’re going through it with the equivalent of a fine-tooth comb. It’s going to take us a very long time."

Weintraub said the search at the DiNardo property is massive and involves major construction equipment, fine sifting equipment and cadaver dogs.

He added: "[The] Montgomery County police academy has leant us their cadets and they are currently assisting us in scouring the fields for any type of evidence that is usable in this type of investigation. The U.S. Marshal, the FBI, police forces all across the county and other counties have now taken part in this. ... This is truly an all-hands-on-deck investigation."

A plea for help

Weintraub said a "ton of leads" have come in and investigators have been able to narrow their focus.

Weintraub said he is encouraged by the pace of the investigation but he urged anyone with information about the men's disappearances to come forward.

"What we’re looking for is information that connects these four men together, that may connect them to the property we’re searching, connect them to Cosmo DiNardo, perhaps," he said. "I can’t say if there is that type of information, but if there is, I beg of you to please give it to us and let us run it down."

"We maintain hope that we will ascertain their whereabouts and bring them home safe," Weintraub said.

He said this afternoon, "We’re committed to see this through all the way to the end, regardless of what that may be."

The Associated Press contributed to this report.

ABC News' Eva Pilgrim and Aaron Katersky contributed to this report.