Police searching the Las Vegas home and office of Michael Jackson’s personal physician seized a compact disc labeled with a pseudonym used by the pop star, a source familiar with the search said Wednesday.

The disc marked “Omar Arnold” contained what appeared to be records of an electrocardiogram Dr. Conrad Murray performed on Jackson while the singer was living in Las Vegas, the source said. Omar Arnold was an alias Jackson had long used in connection with his healthcare.

In search warrants signed by a Las Vegas judge, investigators said they were looking for medical files, billing records, prescriptions and other items relating to Jackson or 19 possible pseudonyms.

LAPD detectives and Drug Enforcement Administration agents also copied four computer hard drives in Murray’s cardiology office and collected phone message pads, the source said.

-- Harriet Ryan