Demolition at the site of a fatal building collapse at 22d and Market Streets resumed Monday, with officers from the police Crime Scene Unit on hand in case pertinent evidence was discovered.

Workers began by removing debris from the lot that once housed a Salvation Army thrift store, flattened this month when an unsupported wall from a demolition site next door toppled. Six people were killed and 14 injured.

Work also was poised to begin next door, where the owner, Richard Basciano, was negotiating to hire a separate demolition outfit.

Basciano, who has long owned significant portions of the 2100 and 2200 blocks of Market Street, recently decided to redevelop the area. The contractor he initially hired to demolish several buildings there, Griffin T. Campbell, was a sole proprietor with a criminal record.

He hired an excavator operator, Sean Benschop, who had a history of drug arrests. A toxicology report found that Benschop, who was injured in the collapse, had marijuana in his system.

Benschop has been charged with six counts of involuntary manslaughter and other crimes.

Control of the parcels, which were considered a crime scene in the weeks after the June 5 collapse, has been returned to the owners, Basciano and the Salvation Army.

The Salvation Army's insurance carrier retained Mellon Certified Restoration of Yeadon to demolish and clear debris from the thrift store parcel.

Tom O'Grady, a property-loss specialist for Mellon, said workers also were seeking to recover personal belongings of victims and Salvation Army employees.

He said the company would work with Crime Scene Unit officers, who were on site Monday but not working in the debris piles.

"Our job is to sift," O'Grady said. "Ours is more involved because we're picking through the rubble."

District Attorney Seth Williams said he would convene a grand jury to consider criminal charges in the case, and a handful of other federal and local investigations are continuing.

Basciano, meanwhile, was negotiating to hire Geppert Bros., a Montgomery County company that works in four states and has done major jobs in the city, including demolition at the site of the Convention Center.

Geppert began preparing for the job on Friday "in good faith," said Mary Pat Geppert, the company's government and media liaison. Company equipment was on site Monday, and work on the Basciano parcel could start by Wednesday, she said.

A spokeswoman for the Department of Licenses and Inspections said both demolition sites were properly permitted.