Prince: Cops Zero in On Minnesota Doctor

A doctor who treated Prince, wrote him prescriptions and was present at Paisley Park when the singer died has mysteriously left the medical center where he worked.

Cops obtained a search warrant for North Memorial Medical Center where Dr. Michael Todd Schulenberg worked. The warrant asks for all medical records, documents, reports, charts, photos, prescriptions, doctor's notes and medical notes for Prince Rogers Nelson.

According to the warrant, cops interviewed Dr. Schulenberg, who acknowledged he treated Prince twice in April ... the last time the day before he died. The doctor told cops he ran tests on the singer and he was at Paisley Park the day Prince died to drop off the test results.

The doctor also told cops he prescribed medications for Prince, which were supposed to be filled at Walgreens.

TMZ broke the story ... Prince had gone to Walgreens 4 times in the week preceding his death. The warrant mentions the plane trip where Prince OD'd 6 days before his death. We broke the story about the emergency landing and that the drug was Percocet.