PENNSYLVANIA, USA (AP) — A 20-year-old linked to a Pennsylvania farm at the centre of a search for four missing men was arrested yesterday on charges he tried to sell one man’s car after he went missing, even as it contained the man’s “life-saving” diabetic kit, authorities said in announcing the first big break in the case.

Tom Meo, 21, never went anywhere without the medicine, a prosecutor said as the search intensified. Meo and two others were last seen in suburban Philadelphia on Friday, while the fourth vanished two days earlier.

Cosmo DiNardo, described as a person of interest, was taken back into custody yesterday on a stolen vehicle charge, and a judge ordered him held on US$5-million cash bail. Less than a day earlier, his father posted 10 per cent of the US$1 million bail set when the son was arrested Monday over an old gun charge. His parents, Antonio and Sandra DiNardo, own the sprawling farm property the FBI and police cadets have been methodically searching for four days.

“The search at the scene is really intensifying,” Bucks County District Attorney Matthew Weintraub said at an afternoon news conference. “I’m very encouraged … that we’re going to get some finality in this just prolonged ordeal.”

According to a police affidavit, police interviewed a man who said DiNardo tried to sell him an old Nissan, the type belonging to Meo, on Saturday, one day after Meo went missing. Police found the car early Sunday on the DiNardo farm, with the keys and title hanging up in a garage.

The DiNardo farm alone covers 90 acres, much of it cornfields. They also own other nearby farm parcels, along with concrete and construction businesses based in Bensalem, about 20 miles (32 kilometres) away, where the son was arrested at the family home.

The FBI has been using heavy equipment to dig a deep ditch on the farm property, then sifting through each bucket of dirt by hand. The search has unearthed “important” evidence, but no human remains, Weintraub said.

He has called the search for the missing men could be “a marathon” given the task at hand.

“We’re going to continue digging and searching that property until we’re satisfied that they are not there,” Weintraub said earlier in the day. “This is just really, really rough on everybody involved because of the heat, the magnitude, the scope — and the stakes are incredibly high, life and death.”

At least some of the missing men are friends, but it’s unclear how well they knew DiNardo, if at all. Online records suggest he was a year ahead of another missing man, 19-year-old Jimi Tar Patrick, at a Catholic high school for boys in Bensalem.

The others missing are 22-year-old Mark Sturgis and 19-year-old Dean Finocchiaro. Sturgis and Meo worked together doing construction for Sturgis’ father, while Finocchiaro was a mutual friend.

DiNardo was arrested Monday on a gun charge that had been dismissed this spring. He is accused of possessing a shotgun and ammunition despite a previous mental health commitment.

DiNardo’s social media posts suggest an avid interest in hunting, fishing and Air Jordan sneakers, which he appeared to sell online. He had enrolled in a nearby college at one point as a commuter student, with hopes of studying abroad in Italy, according to an article on the college website. He had a few other brushes with the law since turning 18 over traffic violations and other minor infractions.

Neither DiNardo’s parents nor his lawyer have commented this week.

The farmland being searched is in the town of Solebury, about 30 miles (48 kilometres) north of Philadelphia.