Law enforcement sources tell TMZ they were called out to the medical office of Michael Jackson's good friend and personal physician, Arnold Klein, to investigate new alleged death threats.
As TMZ first reported, Klein -- along with Jason Pfeiffer, the man claiming to be Jackson's boyfriend -- have gone to the FBI to report the threats. We're told the FBI kicked the case over to the Beverly Hills Police Department, who has now opened up an investigation.
On Thursday, cops were called to Klein's Beverly Hills office after the number of threatening calls intensified. We're told cops took a report.