Erik (The Viking) Fromm, for many years one of the nation's leading amateur bodybuilders, died in his Richfield home from an overdose of a highly potent and addictive painkiller, authorities said today.

Fromm, 36, who died Feb. 4, overdosed on fentanyl, the Hennepin County medical examiner's office said. The office said the overdose was accidental, and police said Wednesday that they expect to close their investigation soon.

Fromm's death is at least the second in the Upper Midwest involving a bodybuilder using fentanyl. The other case was in Sioux Falls, S.D., last spring.

"People can very easily can overdose on it because it is so strong," said Carol Falkowski, director of the Chemical Health Division of the state Department of Human Services and a leading expert in Minnesota on illicit drug use. "It's almost always used in hospital settings, it's so strong."

Fentanyl is an opium-derived pain reliever and is considered at least 80 times stronger than morphine. In 2006, people in major population centers such as the Twin Cities, Philadelphia and Detroit were selling fentanyl on the street as heroin, leading to deaths, Falkowski said. That problem seems to have abated after the arrest of suspects in Chicago, and no new cases have been reported in the Twin Cities since 2006, according to federal authorities.

Fentanyl skin patches were the subject of recent federal recalls because of a flaw that could cause patients or caregivers to overdose.

In 2006, the Food and Drug Administration said that "deaths and other serious problems have resulted from accidental overdoses" of fentanyl.

Fromm had a serious traffic accident about a year ago in Wyoming, causing him severe pain in his lower back and in his legs and arms, said Kevin Schreifels, a friend of Fromm's.

"He was rating the pain pretty high," said Schreifels, a doctor at Lyn-Lake Chiropractic in Minneapolis. He said he was unaware of Fromm using fentanyl.

While living in his native Wyoming and other Rocky Mountain states between 1998 and 2004, Fromm consistently finished in the top 10 among amateur super-heavyweights in national competitions sponsored by the 20,000-member National Physique Committee. He climbed to second in 1999.

Flex magazine reported in 2005 that Fromm suffered physical setbacks -- tearing a biceps and a chest muscle.

In the other bodybuilder's death, 34-year-old Clinton J. Bitz of Sioux Falls died in his sleep in April 2007 from an "acute fentanyl overdose," said his fiancée, Bobbi Doerfler, citing the death certificate.

Doerfler, who moved from Monticello, Minn., with Bitz to South Dakota in 2001, said he suffered from painful migraines and had built up a resistance to other painkillers.

Bitz's mother, Wanda Cyr, of Monticello said that a relative shipped fentanyl patches to her son. She said police in Sioux Falls have been pursuing a criminal case against that relative, who had the patches properly prescribed to him.

Police said they are wrapping up their investigation and could send the case to prosecutors by the end of the week for possible charges.

Cyr said that her son, an electrician who competed in regional bodybuilding events, didn't know that the dosage in the relative's patches had been increased shortly before he last used them.

Cyr, a nurse, said that she told her son: " 'You can't use these. These are dangerous.'"

Paul Walsh • 612-673-4482