British police were on Sunday investigating death threats against BBC director-general Tony Hall following his decision to drop popular "Top Gear" presenter Jeremy Clarkson.
Scotland Yard police headquarters confirmed it was examining allegations made on Wednesday, when Hall confirmed Clarkson's contract would not be renewed at the end of March after he hit a producer.
"Police in Westminster (central London) are investigating an allegation of threats to kill. The allegation was reported to police on Wednesday," a spokesman said.
"Inquiries continue. No arrests have been made."
The Mail on Sunday newspaper said Hall's home had been under 24-hour guard since the threat was received.
The weekly tabloid printed pictures showing security outside, claiming it was costing £1,000 ($1,500, 1,350 euros) a day to protect the corporation's top executive.
A BBC spokeswoman said: "We wouldn't comment on security matters."
"Top Gear" is the world's most popular factual television programme, with 350 million viewers per week in 170 countries.
Clarkson, who was the main presenter, is caricatured by fans as a straight-talking man-of-the-people and by detractors as a boorish bigot.
More than a million people have signed a petition calling for Clarkson to be reinstated.
Clarkson's contract was not renewed after an internal BBC investigation found he physically attacked "Top Gear" producer Oisin Tymon following a lengthy verbal tirade, reportedly because the presenter was annoyed at a lack of hot food after a day's filming.
The 30-second attack saw Clarkson strike the producer, giving Tymon a swelling, bleeding lip.
The outspoken presenter, 54, flagged the incident to the BBC after Tymon took himself to hospital.
Clarkson's departure will have financial implications for the British Broadcasting Corporation, as its commercial arm BBC Worldwide earns around £50 million ($75 million, 70 million euros) a year from the show.