By Walt Hunter

PHILADELPHIA (CBS) — Sources tell CBS 3 the excavator operator involved with Wednesday’s deadly building collapse in Center City will face six counts of involuntary manslaughter.

Sources tell CBS 3 that blood tests on the excavator operator, 42-year-old Sean Benschop, detected the presence of a prescription painkiller and marijuana.

The blood, along with urine, was taken from Benschop at the hospital approximately two hours after the collapse at 22nd and Market Streets, which killed six people and injured 13. (See Related Story)

Sources say investigators also noticed that Benschop, who has a history of 11 prior arrests, including a conviction for possession and dealing drugs, was speaking in what police considered an unusually slow, quiet way, “almost whispering,” according to a source.

Benschop also allegedly told investigators, according to a source, that he was in pain and taking pain medication after recently cutting his finger.

The crane operator, who CBS 3 was not able to contact for comment, is not charged with any wrongdoing in connection with the collapse.

Late Friday afternoon, a search warrant was executed on Benschop’s home. Police took two computers and another box of unknown items.

CBS 3 reported Thursday that two top homicide prosecutors from the Philadelphia District Attorney’s Office were at the collapse scene conferring with investigators, along with crime scene specialists.

A source confirms a criminal investigation may be launched soon. However, a spokesperson for the District Attorney’s Office replied Thursday that it is “too early” to speculate about any possible investigation.