Death threats have been made against the Australian radio hosts at the centre of the royal prank call tragedy, police said on Friday, with the station management reportedly hiring bodyguards and moving staff to safehouses.
Police have launched an investigation after a letter targeting presenter Michael Christian was seized, warning him there were "bullets out there with your name on it".
The letter was obtained by Sydney's Daily Telegraph, which said further threats were made involving a shotgun which it said were inappropriate to print.
The Australian Broadcasting Corporation said staff at 2Day FM's parent company Southern Cross Austereo have been receiving death threats all week following the death of a nurse at a London hospital who fielded the call.
"Police are conducting an investigation into threats made against two Sydney radio presenters," a New South Wales police spokesman told AFP.
"Detectives seized a letter which contained a number of threats. Detectives are conducting an investigation into the matter and are attempting to identify the source of the letter."
Southern Cross Austereo could not reached for comment but the Telegraph said about a dozen staff at the broadcaster have been moved to hotels for their safety and up to 10 executives have been assigned bodyguards.
Christian and fellow host Mel Greig, who have been undergoing counselling, remain off air and have not been seen in public since making tearful apologies on commercial television on Monday.
It follows their call last week, posing as Queen Elizabeth II and Prince Charles, to London's King Edward VII Hospital which was treating Prince William's pregnant wife Catherine.
It was fielded by mother-of-two Jacintha Saldanha, 46. With no receptionist on duty, she put them through to a colleague who divulged details of Kate's recovery from severe morning sickness.
Saldanha was found dead three days later in her nurses' quarters, with an inquest on Thursday revealing she was found hanged. She also had wrist injuries and left three notes.
Senior British police officer James Harman told the inquest there were "no suspicious circumstances" surrounding her death, indicating that no one else was involved.
Australia's media watchdog on Thursday opened an investigation into the prank call to determine whether it breached standards of decency, invaded privacy or contravened the Commercial Radio Codes of Practice.