Toxicology tests showed the 45-year-old musician died from an overdose of fentanyl, Champaign County Coroner Duane Northrup said in a brief news release that noted the drug is found in patches commonly prescribed to treat chronic pain.
The release did not indicate whether Bennett had used such a patch but Northrup told The (Champaign) News-Gazette that Bennett had a patch containing fentanyl on his back when he died May 24 after being found unresponsive in his home in Urbana, 110 miles south of Chicago.
Northrup did not return a call from The Associated Press and his office declined to immediately provide a copy of Bennett's autopsy, saying the investigation remains open.
Several companies recalled fentanyl patches last year after discovering that some leaked, causing labored breathing and possible overdose. There was no indication Bennett had used a recalled patch.
In a recent posting on his MySpace page, Bennett wrote that he was getting ready for hip replacement surgery after years of pain.
"As time has passed my mobility has continued to erode, to the extent that, for quite some time now, it has even been difficult to sit at the computer for more than just a few minutes," Bennett wrote in a posting dated April 25.
Members of Bennett's family could not immediately be located for comment. There was no immediate response to an e-mail sent to his record company.
Bennett worked as a sound engineer and played instruments for Wilco from 1994 to 2001.
He sued Wilco lead singer Jeff Tweedy in early May. Bennett claimed he was owed royalties for songs during his seven years with the group.
After learning of Bennett's death Tweedy said Bennett made significant contributions to Wilco and said he would be remembered "as a truly unique and gifted human being."
Bennett was born in the Chicago suburb of Rolling Meadows and graduated from the University of Illinois in Urbana-Champaign.
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