Music superstar Prince's death from an opioid overdose is a stunning example of a national epidemic of overdose deaths driven by prescription opioid painkillers.

Prescription opioid overdoses reached nearly 19,000 in 2014, the highest number on record. Total opioid overdoses surpassed 29,000 that year when combined with heroin, which some abusers switch to after becoming hooked on painkillers.

A law enforcement official told The Associated Press on Thursday that tests show the music superstar died of an opioid overdose. The 57-year-old singer was found dead April 21 at his Minneapolis-area estate.

The official, who is close to the investigation, spoke on condition of anonymity because he was not authorized to speak to the media. Authorities haven't yet released autopsy results.