Law enforcement officials were back at the DiNardo family's sprawling Solebury Township property on Thursday, continuing with this week's clean-up efforts on the 90 acres where prosecutors say Cosmo DiNardo killed and buried four men earlier this month.

Bucks County District Attorney Matthew Weintraub said activity on the farmland increased Thursday morning in preparation for a possible release of the crime scene.

"Because of that, and because renewed probable cause would be required for us to revisit the property once it is released to its owners, we want to make absolutely certain that we have not missed any evidence before departing," Weintraub said.

Philadelphia police were among those at the DiNardos' property, under the direction of Bucks County officials, a police spokesman said.

Philadelphia police had said they would investigate DiNardo's claims that he killed two other people in Philadelphia — if they got more information from Bucks County investigators. There was no indication Thursday that the increased activity on the DiNardo's Solebury property was connected to those claims.

Weintraub said they were conducting a "comprehensive walk-through" of the site where the four bodies were found last week. He said Thursday's activity included "a large number of law enforcement personnel, police cadets and others, including horses and dogs" because of the size of the farmland on Lower York Road.

A week after Cosmo DiNardo's confession to investigators, the walk-through marked the latest activity at the property where prosecutors say the 20-year-old Bensalem native shot and killed four men whom he lured there by saying he would sell them marijuana. The men's disappearance set off the largest criminal investigation in recent Bucks County history and garnered national attention.

DiNardo, who has confessed to killing four men at the property, also told authorities that he killed two other people, a male and a female, both in Philadelphia, when he was 15. Philadelphia police said Wednesday they were investigating the claim but had very little information to proceed and were waiting for Bucks County officials to disclose more details.

The Fox29 footage showed several police vehicles parked near a house on the property around 10:30 a.m. Thursday.

The District Attorney's Office this week had been working to clean up the scene where law enforcement searched last week for the remains of four young men who went missing earlier this month. A mass grave more than 12-feet deep containing the remains of three victims was discovered and farther away, a second deep grave with the fourth victim.

DiNardo confessed last Thursday to the killings of Jimi T. Patrick, 19, of Newtown; Dean A. Finocchiaro, 19, of Middletown Township; Thomas C. Meo, 21, of Plumstead Township; and Mark P. Sturgis, 22, of Pennsburg, Montgomery County. Prosecutors say Dinardo, 20, from Bensalem, with help from his cousin Sean Kratz, also 20, lured the men to his property under the guise of selling them marijuana. He admitted shooting and killing them and burying the bodies on his parents'  90-acre property.

Inquirer reporter Justine McDaniel contributed to this report.