06/09/2009 at 04:45 PM EDT
Las Vegas entertainer Danny Gans died from a toxic reaction to medication he was taking for chronic back pain, the coroner announced Tuesday.
Gans, 52, was using the prescription drug hydromorphone, commonly known as Dilaudid, at the time of his May 1 death
, says Clark County Coroner Michael Murphy.
"This is not an issue of drug abuse," Murphy said, though he would not say what the level of Dilaudid was.
Gans's unexpected death sparked rumors of drug use – rumors his management fought vigorously to dismiss.
Gans's spot-on impersonations of celebrities made him a popular headliner on TV and in Las Vegas. He had recently signed a contract to appear exclusively at Encore Las Vegas, and had previously played at the Mirage and Rio.