Dr. Michael Schulenberg, who reportedly treated Prince before his death, has been described as missing as authorities intensify their investigation into the singer’s cause of death. Above, Prince appears at the 2015 American Music Awards presentation in Los Angeles Nov. 22. Getty Images

Law enforcement authorities are searching high and low for Dr. Michael Schulenberg, the family medicine physician who reportedly treated Prince before his death. Police apparently have obtained the warrants necessary to seize documents as well as other materials linked to the doctor, but they’ll have to find him first.

According to TMZ, Schulenberg has been missing in action for days. He is believed to have abruptly left his office at the North Memorial Clinic in Minnetonka, Minnesota, within “the last few days.” Sources close to the physician have claimed Schulenberg did not say whether he was fired or left of his own volition. The media outlet reported he met with Prince April 7 and April 20, the day before the famed performer’s tragic death.

Schulenberg reportedly wrote prescriptions for the “Purple Rain” singer, which were filled at a Walgreens pharmacy he frequented. In fact, Prince is believed to have visited the pharmacy four times in the week before his death, although it remains unclear which medications he was picking up.

It is conceivable Schulenberg and Prince also may have had previous contacts. TMZ reported the doctor worked in association with Ridgeview Hospital before assuming his latest position. And it said the performer’s bodyguard claimed the singer visited that hospital in 2014 and 2015.

More than a dozen police cars were seen Tuesday arriving at Prince’s Paisley Park mansion in Chanhassen, Minnesota. According to local reporter Angela Davis’ Twitter account, authorities were on the premises in search of medical records after receiving the appropriate permission. Carver County detectives obtained a search warrant after Schulenberg said he had prescribed medication to Prince two weeks before the singer died, the Los Angeles Times reported.

It remains unclear whether all four prescriptions Prince filled in the seven days before his death were provided by Schulenberg. TMZ reported April 29 that the Grammy Award winner may have “doctor shopped,” allowing him to obtain multiple prescriptions for Percocet, the controlled substance to which he is rumored to have been addicted. There also has been speculation Prince may have used false names to fill the prescriptions, although it is unconfirmed.

Prince’s official cause of death remains unknown. The Midwest Medical Examiner’s Office in Ramsey, Minnesota, released a statement May 5 addressing rumors that the pop icon had overdosed. The office assured fans it had released no definitive cause of death, adding that “results are pending” and the investigation is “ongoing.”