No criminal charges will be filed in the 2016 death of pop star Prince, prosecutors say.

After a two-year inquiry, prosecutors in Minnesota announced they found no evidence of intentional wrongdoing in the the singer’s death, reporting a self-administered overdose of painkillers as the cause.

“We simply do not have sufficient evidence to charge anyone with a crime related to Prince’s death,” Carver County Attorney Mark Metz told a news conference on Friday (Thursday local time).

However, Mr Metz added that Prince may not have known he was taking a counterfeit Vicodin painkiller, which was found to be laced with potentially deadly fentanyl – an opioid 50 times stronger than heroin.

“Nothing in the evidence suggests Prince knowingly ingested fentanyl,” Mr Metz said.

“In all likelihood Prince had no idea he was taking a counterfeit pill that could kill him.”

Prince, 57, was found dead at his Paisley Park home and recording studio complex near Minneapolis on April 21, 2016.

Prosecutors said they found counterfeit pills containing fentanyl in his home, but were unable to determine the source.

“There is no reliable evidence showing how Prince obtained the counterfeit Vicodin laced with fentanyl or who else may had a role in delivering the counterfeit Vicodin to Prince,” Mr Metz said.

Investigators found evidence that Prince suffered from severe pain for a number of years and that hundreds of various sorts of painkillers were found in his residence, according to Mr Metz.

The probe included searches of Prince’s computer, mobile phone records of his friends and interviews with associates.

Some of the pills were prescribed to his bodyguard, Mr Metz said, to protect the singer’s privacy.

But he said there was “no evidence that the pills that killed Prince were prescribed by a doctor”.

It was also revealed the doctor in question had paid a $US30,000 ($39,000) fine as part of a civil settlement over accusations of illegally prescribing painkillers to Prince, BBC reported.

Investigators said however this was not the drug that killed the pop star.

–with agencies