A toxicologist who worked on Michael Jackson's autopsy said Thursday that trace amount of Propofol was found in Jackson's stomach after he died, but no illegal drugs were found in the pop superstar's system.

As the involuntary manslaughter trial against Jackson's personal physician entered eighth day of deliberations, Dan Anderson, a supervising criminalist working with the Los Angeles County Coroner's Office, told the seven-man, five-woman jury that tests showed positive toxicoloy findings for seven drugs in Jackson's system, including Propofol.

Jackson also tested positive to lidocaine, diazepam (Valium), nordiazepam (a metabolite of Valium), lorazepam (Ativan), midazolam (Versed) and ephedrine.

Propofol and lidocaine were detected in a syringe retrieved from a table near the singer's bed, Anderson testified.

Tests on another syringe and IV tubing found four days after his June 25, 2009 death further showed traces of Propofol, lidocaine and flumazenil, Anderson told the court.

Anderson said that "negligible" amount of Propofol was also detected in a jug filled with urine which was collected from the pop icon's bedroom, but he could not draw any conclusions as its source could not be established.

No illegal substances were found in the singer's system, he noted.

The toxicologist is due back on Friday for more questioning.

In earlier testimony, a coroner's investigator defended the way she documented and collected evidence from Jackson's rented mansion after the singer's death, while acknowledging that she moved a medicine vial before photographing it and left her thumbprint on a syringe.

Elissa Fleak conceded that she picked up a bottle of the medication flumazenil from the floor of Jackson's bedroom and moved it to a bedside table before any photographs were taken, under questioning from Murray's defense attorney Edward Chernoff. She also acknowledged that she left a partial thumbprint or fingerprint on a syringe found in the room.

"Would you agree you made a substantial number of mistakes in your investigation?" Chernoff asked.

"No," Fleak replied.

The investigator testified on Wednesday that she had found 12 vials of the anesthetic Propofol along with a variety of prescription drugs, lotions and medical supplies from the singer's home after his death.

Prosecutors seek to prove Murray, 58, failed to properly monitor Jackson after giving him a lethal dose of Propofol. They contend that the cardiologist "repeatedly acted with gross negligence, repeatedly denied care, appropriate care to his patient, Michael Jackson," and that it was his repeated incompetence and unskilled acts that led to Jackson's death.

Defense attorneys argued Murray was weaning Jackson off the medication, but the singer "self-administered" a lethal dose. The cardiologist was hired by Jackson to care for him during his comeback series of 50 sold-out concerts.

The trial is expected to last four to five weeks. Murray, who is set free on a bail of 75,000 U.S. dollars, faces up to four years in prison if convicted of the felony charge.