A former nurse who has already pleaded guilty to killing 17 patients in New Jersey and Pennsylvania will be charged in at least six more cases, state police said Thursday.

The charges stem from Charles Cullen's (search) work at hospitals and a nursing home in Lehigh County (search) from late 1998 to 2000, said Capt. Scott Snyder, who is leading the Pennsylvania investigation. Defense lawyer Gary Asteak said he expected murder and attempted murder charges.

Cullen once claimed to have killed 30 to 40 people. He agreed to help investigators identify his victims in exchange for a death penalty reprieve.

Victims' relatives were called to a meeting Wednesday night at state police barracks in Bethlehem to learn of the pending charges.

"It was very unsettling, but it was also positive in a certain aspect," Snyder said. "I think it provided some much-needed relief for the loved ones of the deceased."

Snyder said the charges would involve six to 10 cases at institutions including St. Luke's in Fountain Hill and Lehigh Valley Hospital (search). He declined to offer more detail before an afternoon news conference.

Asteak said his client had thoroughly examined case records provided to him, acknowledging participation in some cases and denying any memory of others.

Cullen pleaded guilty last week in neighboring Northampton County to first-degree murder for the December 1998 death of 78-year-old Ottomar Schramm. In New Jersey, he pleaded guilty to killing 16 people and attempting to kill two others at Somerset Medical Center (search) and Warren Hospital.

Other cases remain under investigation, Snyder said.