Cadaver dogs led investigators this week to the spot on the family farm where they discovered human remains inside a 3.7-metre deep common grave.
Cosmo Dinardo's attorney, Paul Lang, said Dinardo made the confession to Bucks County District Attorney Matthew Weintraub and told investigators where the bodies were buried in exchange for avoiding the death penalty, reported Reuters.
"We here are utilizing every resource at our disposal to try to find these four missing men and to solve this case", Weintraub said.
Police found Meo's Nissan at 4 a.m. on Sunday on a property owned by the Dinardos.
The person with knowledge of the confession said one of the men was killed July 5 and the other three were killed July 7. According to the arrest report, DiNardo suffers from mental illness and had been involuntarily committed to a mental institution at that time.
DiNardo is being held on $5 million cash bail after authorities charged him with allegedly stealing Meo's vehicle and attempting to sell it.
DiNardo is a person of interest in the four disappearances and was previously been taken into custody on an unrelated gun charge, authorities said.
Earlier Thursday, investigators worked to excavate a 12-foot grave found to hide human remains on the 90-acre farm.
"We're going to bring each of these lost boys home to their families, one way or another", Weintraub said.
DiNardo is reportedly being held on $5 million cash bail.
Finocchiaro, Meo and Sturgis all knew each other, the AP reported, and news outlets have reported that cars belonging to two of the men have been located.
Taking a few questions from reporters, Weintraub said investigators continue to examine the evidence in the case. "We're going to keep digging and searching that property until we are satisfied that they are not there".