Toxicology test results show that Virginia Tech gunman Seung-Hui Cho had no drugs of any kind in his system the day he fatally shot 32 people and himself, state police said Thursday.

"There were no prescription or toxic substances in his system as of April 16, 2007," said state police spokeswoman Corinne Geller. "Basically his system was clean."

Geller added that investigators did not recover any prescription medicine among Cho's effects, and Virginia State Police Superintendent Steve Flaherty has said there was no indication that Cho was on any medication.

The toxicology results would seem to discount speculation that antidepressants might have been to blame for the shootings.

"I would say that drugs probably did not play a role in his actions on that particular day," said Doug Rollins, a toxicologist at the Center for Human Toxicology at the University of Utah. "Most of those drugs, once they're not in the bloodstream, they're not having a pharmacological effect."

The question of whether antidepressants contributed to the shootings was raised after some media outlets reported that Cho took prescription medication.

The Citizens Commission on Human Rights, a nonprofit watchdog group, released a statement the day after the shootings criticizing Congress for failing to investigate a link between psychiatric drugs and school violence.

Marla Filidei, vice president of the organization, said Thursday that Cho's toxicology report should be released so experts can know the extent of the testing.

Geller said, "It was a comprehensive test."

Cho's toxicology results are part of his autopsy report from the state medical examiner's office in Roanoke. The autopsy also confirmed that Cho died from a self-inflicted gunshot wound, Geller said.

The 23-year-old English major from Centreville fatally shot two students at West Ambler Johnston Hall, police said, and another 30 people inside Norris Hall before putting a gun to his own head.

State police also have received autopsy reports for each of Cho's victims, Geller said.

State police and the state's medical examiner system declined to provide a copy of Cho's autopsy documents. Geller cited the ongoing police investigation, and Rochelle Altholz, a state administrator for the medical examiner system, said the report was a medical record protected under state law.

Gerald Massengill, chairman of a gubernatorial panel investigating the Tech shootings, said the panel has informally asked the medical examiner system for Cho's autopsy report.

Massengill also commented on the significance of Thursday's release of Cho's toxicology results.

"I think it's a question that needed to be answered -- what type of medication, if any, was he on?" he said. "We have had public input that suggested to the panel that we should look very closely at antidepressants."