Updated

A second person of interest was taken into custody late Thursday in the investigation into the gruesome murders of four men on a secluded farm in Pennsylvania.

The unidentified person was detained in northeast Philadelphia, Fox 29 reported.

The detention comes on the heels of Cosmo DiNardo’s attorney saying that his client admitted to killing the four men and telling authorities the location of the bodies.

The Associated Press, citing a person with firsthand knowledge of his confession, reported the DiNardo had a co-conspirator.

Paul Lang, DiNardo's lawyer, told reporters earlier Thursday DiNardo, 20, is ready to plead guilty four counts of first-degree murder. Lang said in exchange for the confession, prosecutors agreed to take the death penalty off the table.

missing pennsylvania man cosmo dinardo

Cosmo DiNardo arrested on Monday, July 10, 2017. (Bucks County District Attorney's Office via AP)

“I’m sorry,” a shackled DiNardo said as he left the courthouse.

Prosecutors have not confirmed Lang's announcement, but the AP reported that DiNardo killed the four separately after selling them marijuana, and then burned their bodies at his family's farm.

The source spoke to The Associated Press on the condition of anonymity because he wasn't authorized to publicly discuss details of the case.

The source said the men were killed after DiNardo felt cheated or threatened during three drug transactions. DiNardo sold quarter-pound quantities of marijuana for several thousand dollars and sold handguns to area residents, the person said.

Multiple sets of human remains were unearthed from a 12-foot-deep mass grave on an isolated Pennsylvania farm early Thursday as authorities continued digging for the bodies of four young men who disappeared last week.

Officials were able to identify one of the victims as 19-year-old Dean Finocchiaro -- who vanished last week along with Mark Sturgis, 22, Tom Meo, 21, and Jimi Tar Patrick, 19. Bucks County District Attorney Matthew Weintraub said he could not identify the other remains at this time, while issuing a fresh appeal for more help from the public.

Fire and rescue crews on Thursday were using plywood to help shore up the deep grave as investigators worked inside under intense heat and choking dust.

DiNardo was arrested Wednesday for allegedly trying to sell Meo's car for $500 on July 9 -- a day after Meo was last seen. That 1996 Nissan Maxima was also found on the family's farm.

Fox News’ Travis Fedschun and the Associated Press contributed to this report.

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