Staff at a radio station behind a hoax call that led to the apparent suicide of nurse Jacintha Saldanha have been moved to safehouses, according to reports.
Managers at Sydney radio station 2Day FM have also recruited 24-hour bodyguards to protect employees.
Ms Saldanha was found dead days after the DJs Mel Greig and Michael Christian called London's King Edward VII hospital, where the Duchess of Cambridge was being treated for severe morning sickness.
They impersonated the Queen and Prince Charles, with the "monarch" making enquiries about her "granddaughter".
Australian news website news.co.au said police have launched an investigation due to staff receiving death threats, with one letter specifically targeting Mr Christian.
The letter reportedly said there are "bullets out there with your (Mr Christian's) name on" and contained further threats involving a shotgun.
An inquest into the 46-year-old nurse's death opened at Westminster Coroner's Court on Thursday, and heard injuries were found on her wrists and that she had left three notes.
Two of the notes were found in her room at the hospital. The other was among her possessions.
The mother-of-two's body was released to undertakers on behalf of the family after the hearing.
The court heard that police are exploring emails and texts sent by Ms Saldanha, who was discovered by a colleague and a security guard on Friday.
Officers are also interviewing her friends and family, and staff at the Australian radio station responsible for the prank.
Detective Chief Inspector James Harman said: "On Friday December 7 Jacintha Saldanha was found by a colleague and a member of security staff. Sadly she was found hanging.
"There were also injuries to her wrists. The London Ambulance Service was called to the scene. At this time there are no suspicious circumstances."
The inquest came as pressure mounted on bosses at the radio station to name the executives responsible for airing the hoax call.
Sky News understands Australia's independent media watchdog, the Australian Communications and Media Authority (ACMA), has had 2,500 complaints from around the world over the 2Day FM segment.
ACMA has announced a rare fast-track investigation into the prank, which saw Ms Saldanha put two radio hosts through to a fellow nurse who unwittingly revealed details about Kate's treatment.
Australia's radio broadcasting code stipulates that it is a breach to record a person in conversation, and also air it, without their knowledge.
The radio station insists it did not break the law and says it tried to contact the hospital on five separate occasions. The hospital disputes any contact was ever sought.