Lawyers for Michael Jackson's doctor said on Thursday they were negotiating his surrender to Los Angeles authorities, amid reports he could face an involuntary manslaughter charge within a day.

Dr. Conrad Murray, who has admitted giving the late pop singer a dose of the powerful anesthetic propofol as a sleep aid, is expected to be formally charged on Friday with involuntary manslaughter, celebrity website TMZ.com reported.

Murray's lawyer, Ed Chernoff, declined comment on specifics but said in a statement on his legal firm's website: "We are presently negotiating with the District Attorneys' office the surrender of Dr. Murray. The specifics have not yet been agreed to and when the agreement is complete we will report further on this website."

The Los Angeles District Attorney's office was not immediately available for comment.

Murray, who was at Jackson's house at the time of his June 25 death, has been a focus of criminal investigations for months. The Los Angeles coroner's office ruled that Jackson's death was a homicide, caused principally by propofol and the sedative lorazepam. A cocktail of other painkillers, sedatives and a stimulant were also found in his body.

Murray, a cardiologist, has repeatedly insisted he did nothing wrong and has told investigators he was not the first doctor to give Jackson propofol, according to court records.

Murray was hired in May 2009 to care for Jackson, 50, while the entertainer prepared for a series of comeback concerts aimed at reviving a career sidelined by his 2005 trial and acquittal on charges of molesting a 13 year-old boy.

Jackson's sudden death prompted a worldwide outpouring of grief for the singer, who started his career as a child and whose 1982 album "Thriller" remains the world's best-selling album.