The Hillsborough County medical examiner's office previously determined that the bearded, boisterous TV spokesman had a heart attack in his sleep. His wife found him unresponsive in bed in their Tampa condo June 28.
Mays, 50, was a pop-culture fixture with his energetic commercials pitching gadgets and cleaning products like Orange Glo and OxiClean.
While heart disease was the primary cause of death, a report released Friday by the medical examiner listed cocaine as a "contributory cause of death."
The medical examiner "concluded that cocaine use caused or contributed to the development of his heart disease, and thereby contributed to his death," the office said in a press release.
The office said Mays last used cocaine in the few days before his death but was not under the influence of the drug when he died. Hillsborough County spokeswoman Lori Hudson said nothing in the toxicology report indicated the frequency of Mays' cocaine use.
"We were totally unaware of any non-prescription drug usage and are actively considering an independent evaluation of the autopsy results," Mays' family said in a statement.
The statement said the family was "extremely disappointed" by the release of the information by the medical examiner's office. The report "contains speculative conclusions that are frankly unnecessary and tend to obscure the conclusion that Billy suffered from chronic, untreated hypertension, which only demonstrates how important it is to regularly monitor one's health."
Cocaine can raise the arterial blood pressure, directly cause thickening of the left wall of the ventricle and accelerate the formation of atherosclerosis in the coronary arteries, the release said.
The toxicology tests also showed therapeutic amounts of painkillers hydrocodone, oxycodone and tramadol, as well as anti-anxiety drugs alprazolam and diazepam. Mays had suffered hip problems and was scheduled for hip-replacement surgery the day after he was found dead.
Longtime friend and colleague AJ Khubani, founder and CEO of the "As Seen on TV" product company Telebrands, said Mays never exhibited any signs of drug use and was always prepared for his many commericial shoots.
"I'm just shocked," Khubani said. "He was the model of a responsible citizen."
Mays, a McKees Rocks, Pa., native, developed his style demonstrating knives, mops and other "As Seen on TV" gadgets on Atlantic City's boardwalk. For years he worked as a hired gun on the state fair and home show circuits, attracting crowds with his booming voice and genial manner.
He got his start on TV on the Home Shopping Network and then branched out into commercials and infomercials. He developed such a strong following that he became the subject of a reality TV series, Discovery Channel's "Pitchmen."