Officials at St. Luke's Hospital in Fountain Hill are looking at the deaths of four patients who died while nurse Charles Cullen worked at the hospital.

Cullen has admitted killing up to 40 patients in a 16-year career that hopscotched through the Lehigh Valley and central New Jersey.

St. Luke's spokeswoman Susan Schantz said Monday that 18 families whose members were treated at the hospital have contacted the hospital. All but four patients have been discounted, either because they weren't hospitalized during Cullen's two-year employment or they were not treated in the critical care unit where Cullen worked.

The deaths of the four patients who could have had contact with Cullen during their stays in the critical care unit are being investigated by the hospital, Schantz said. As of Monday, she said the hospital hadn't determined the circumstances of their visits or whether anything appeared suspicious.

The revelation by the hospital came after St. Luke's annual board meeting Monday. During an executive session on Cullen following the meeting that lasted nearly two hours, the Rev. Doug Caldwell, board chairman, said the board had an ''exhaustive'' discussion in which ''we discussed all the details.''

Cullen, 43, of Bethlehem, was charged Dec. 15 with first-degree murder and first-degree attempted murder in the deaths of two New Jersey patients — a Hunterdon County priest and a Basking Ridge cancer patient — at Somerset Medical Center in Somerville.

His claim to have killed up to 40 patients has reopened investigations into patient deaths in the Lehigh Valley. Cullen worked at nine hospitals and a nursing home in the Lehigh Valley and New Jersey since 1987.

Meanwhile, the Pennsylvania Board of Nursing announced Monday that it temporarily suspended Cullen's license pending further investigation.

Brian McDonald, a spokesman for the Department of State, said he could not comment on whether the nursing board acted on previous complaints about Cullen reportedly received from St. Luke's and Liberty Nursing and Rehabilitation Center in Allentown.

McDonald was also unable to say whether Cullen's 1994 application for a Pennsylvania license included information about a guilty plea for breaking into the Palmer Township home of a friend. McDonald said Cullen's application was one of several hundred destroyed in a fire years ago while awaiting microfilming.

In New Jersey, prosecutors investigating Cullen in five counties will coordinate their work through the state attorney general's office, and the state's top law enforcement officer hopes to extend that cooperation to Pennsylvania.

New Jersey Attorney General Peter C. Harvey said Monday that either he or Vaughn McKoy, director of his criminal justice division, will contact Lehigh County District Attorney James Martin and Northampton County District Attorney John Morganelli as early as today.

''We have to talk about it, find out what their concerns are, what stages their cases are in and their views about seeking the death penalty against Mr. Cullen,'' Harvey said.

Martin said he wouldn't comment ''until I hear from the guy and see what's on his mind.'' Morganelli could not be reached for comment.

Prosecutors from Warren, Hunterdon, Somerset, Morris and Essex counties met with Harvey for about 90 minutes Monday before he announced the coordinated investigation. The appointed county prosecutors — who answer to Harvey under New Jersey's judicial system — will pursue their own local probes but will assign one assistant prosecutor and a detective to the coordinated effort. Harvey stopped short of calling it a task force.

He also said it was unlikely that his office would take over prosecution of the local cases.

Cullen's public defender has told prosecutors his client will provide the names of his victims only if prosecutors do not seek the death penalty. Harvey said he couldn't comment on that, but said the involvement of the Lehigh and Northampton prosecutors would be a factor in any decisions.

Harvey said Cullen's mental state also will be a factor in any prosecution. Cullen is now undergoing psychiatric evaluation at the Ann Klein Forensic Center in Trenton, but he has a history of attempted suicide and depression, according to court records.

''It could put in jeopardy the ability to get a conviction,'' Harvey said. ''We are trying to find as many facts as objectively as possible without his cooperation.''