(CNN) None of the medications found in Prince's home following his death last year were prescribed to him , according to court documents unsealed Monday.

Bottles of opioid painkillers -- some prescribed to Prince's former drummer and longtime friend Kirk Johnson -- were found in several places in Paisley Park, and many medications were found in vitamin pill bottles and in envelopes, search warrants showed.

Dr. Michael Todd Schulenberg said he wrote an Oxycodone prescription for Prince under Johnson's name for privacy purposes, according to a search warrant that was among the documents unsealed. A search of the Minnesota Prescription Monitoring Program showed that Prince had no prescriptions issued under his name, and that Johnson only had that one, the warrant said.

In a statement Monday, Schulenberg's attorney said the doctor was cooperating with the investigation and denied prescribing opioids to Prince or "any other person with the intent that they would be given to Prince."

The details from those documents show the possible direction of the criminal investigation into Prince's accidental overdose death almost exactly a year ago, a death that left fans around the world heartbroken and bewildered.

But the circumstances that led up to his death remain a mystery. Among the unanswered questions haunting those who loved and admired him: Who supplied Prince with the painkiller that killed him? Did he know what he was taking? And how long was he taking opioid pain medication?

No one has been charged in connection with his death, but authorities say the investigation is still open and active.

Fentanyl is the strongest painkiller on the market, estimated to be at least 50 times more potent than morphine and at least 30 times more potent than heroin.

According to one of the unsealed search warrants, investigators did not find fentanyl among the cache of pills, many of which were hidden in bottles labeled "Bayer" and "Alleve."

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According to another search warrant issued April 21, 2016, the same day Prince was found dead at his home in Chanhassen, Minnesota, investigators found several pills labeled "Watson 853" -- hydrocodone-acetaminophen, sometimes called Vicodin -- and capsules marked "A-349," which is Percocet, in different bottles in various locations in the residence.

Also according to the search warrant, investigators were told by witnesses that Prince "recently had a history of going through withdrawals which are believed to be the result of abuse of prescription medication."

Federal prosecutors and the Drug Enforcement Administration are investigating how Prince obtained prescription medications and from whom. Because Prince had no prescriptions issued in his name, investigators sought access to email servers to see if he purchased them via email, according to the documents.

Pills found in suitcase

Search warrants and other documents related to criminal cases are normally public record, but authorities had requested all documents related to the Prince death investigation be sealed as the probe proceeded. Authorities asked that the search warrants be sealed "until April 17, 2017 or when a criminal case may be instituted, whichever occurs first."

Information in the warrants also revealed that investigators found a suitcase containing several prescription bottles in the name of Johnson, who told investigators last year that the singer had been struggling with opiate use.

The suitcase also contained the lyrics for "U got the Look," which appeared to be in Prince's handwriting. The suitcase had a tag on it bearing the name "Peter Bravestrong," which investigators determined is an alias for Prince.

CNN's attempts to reach Johnson on Monday were not immediately successful.

Schulenburg is a local doctor who arrived at Paisley Park after the singer's body was found in an elevator inside the complex, according to the documents.

The doctor left his job at North Memorial Medical Center nearly three weeks after Prince's death.

According to a search warrant, Schulenberg told investigators he saw Prince on April 7 and April 20, and prescribed medications for Prince to be picked up at a Walgreens pharmacy. He went to Paisley Park on April 21 -- the day Prince was found -- to drop off test results, he said.

Schulenberg said Monday he did not prescribe any opioid painkillers to Prince.

"Dr. Schulenberg has been and remains committed to providing full transparency regarding his practice as it relates to the Prince investigation," his lawyer, Amy Conners, said in a statement.

"Dr. Schulenberg has previously disclosed all information regarding his care and treatment of Prince to his former employer, law enforcement authorities and regulatory authorities in the course of his complete cooperation with the investigation of Prince's death."

"There are no restrictions on Dr. Schulenberg's medical license, and contrary to headlines and media reports published in the wake of today's unsealing of search warrants relating to the investigation, Dr. Schulenberg never directly prescribed opioids to Prince, nor did he ever prescribe opioids to any other person with the intent that they would be given to Prince," Conners said.

Photos: Stars loved Prince Alicia Keys considered Prince "a gift." In 2009 Keys covered Prince's "How Come U Don't Call Me Anymore?" and on the day he died, April 21, paid tribute to him at the Tribeca Film Festival. Hide Caption 1 of 10 Photos: Stars loved Prince The singer inspired actress Jada Pinkett Smith to play by her own rules. Hide Caption 2 of 10 Photos: Stars loved Prince Mick Jagger mourned the loss of a "revolutionary artist." Hide Caption 3 of 10 Photos: Stars loved Prince Janelle Monae was a protege of Prince and called him fearless. Hide Caption 4 of 10 Photos: Stars loved Prince In 2015, singer Miguel said Prince was an inspiration to him. Hide Caption 5 of 10 Photos: Stars loved Prince President Barack Obama paid tribute to the late singer after his death on April 21. Hide Caption 6 of 10 Photos: Stars loved Prince QuestLove has perhaps one of the best Prince stories ever, which has gone viral. The drummer/producer said he's patterned his life after the artist. Hide Caption 7 of 10 Photos: Stars loved Prince Carlos Santana took to Twitter a few days after Prince's death to offer up a spiritual message. Hide Caption 8 of 10 Photos: Stars loved Prince Stevie Wonder admired the versatility of Prince. He and Madonna paid tribute to the late star during the Billboard Music Awards in May. Hide Caption 9 of 10 Photos: Stars loved Prince Justin Timberlake said he was a lifelong Prince fan and paid tribute to him on social media. Hide Caption 10 of 10

Last show and an emergency landing

About a week before his death, Prince's private jet made an emergency landing early April 15 in Moline, Illinois, on the way back from a performance in Atlanta. His publicist reassured fans that the 57-year-old star was fine, but a May 6 search warrant said investigators spoke to a witness who said Prince was rushed to a hospital because he was unconscious, and that the singer had admitted to taking one or two pain pills.

The day before Prince died, his team called an eminent opioid addiction specialist in California seeking urgent help for the singer, an attorney working for the specialist and his son said.

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The specialist, Dr. Howard Kornfeld, couldn't get there immediately so he sent his son, Andrew Kornfeld, on an overnight flight to Minnesota. The goal was for the younger Kornfeld to help evaluate Prince's health and encourage him to enter treatment for pain management and potential addiction issues, attorney William Mauzy told reporters.

But by the time Andrew Kornfeld arrived at the singer's Paisley Park complex on the morning of April 21, it was too late. He and five others were searching for Prince when Kornfeld said he heard a scream . He ran down the hall and found the 57-year-old entertainer unresponsive in an elevator. Andrew Kornfeld was the person who called 911, Mauzy said.

Prince's body was later cremated. Although the medical examiner's office released the cause of death, the full toxicology report was not -- and will not be -- released.

Signs of trouble?

Nearly everyone who was close to Prince -- and who has been willing to speak to the media -- said they never saw him taking any drugs. "He was the healthiest man I knew," a bodyguard known as "Romeo" told CNN.

That narrative is slowly beginning to change. In a new memoir called "The Most Beautiful," Prince's first wife, Mayte Garcia, said she never saw him take drugs, but she did say the singer once asked her to go up to his hotel room and "flush some pills." She said she didn't question what they were.

On another occasion, within weeks of their 1996 wedding, Garcia said she was informed that Prince was in the hospital and had to have his stomach pumped. Her husband explained that he had mixed wine with aspirin, she said.

She also writes of the couple's devastation after their first child died soon after birth and recounts noticing that her "Vicodin kept disappearing." They divorced in 2000.

And the former attorney for two of Prince's dead siblings says they had revealed Prince had an addiction to Percocet decades ago.

Prince's half-brother, Duane Nelson, said he used to get the drug for Prince to help him come down after shows, attorney Michael B. Padden said. Nelson died in 2013.

Another half-sibling, Lorna Nelson, also alleged drug use by Prince but was not involved in getting drugs for him, Padden said. She died in 2006.