"Police in Westminster are investigating an allegation of threats to kill," the Metropolitan Police confirmed to CNN in a statement.
The allegation was reported to the police on Wednesday.
"The threat was made by email," the police added. "The content of the message suggests (it was sent) from outside the UK."
"Top Gear" was suspended
March 10 after an apparent altercation between the motor show host and producer Oisin Tymon on March 4. At the time, the BBC issued a statement
saying that there had been a "fracas" between the host and a BBC producer.
More than 1 million fans of Clarkson and "Top Gear" signed a petition
to reinstate the host. The document was delivered to the BBC's headquarters
by a fan dressed as the "Stig" -- the incognito racing car test-driver who appeared regularly on the show -- driving an armored tank.
On Wednesday, the British broadcaster announced that it would not be renewing Clarkson's contract as host of "Top Gear"
after he allegedly busted his producer's lip and hurled verbal abuse at him.
"It is with great regret that I have told Jeremy Clarkson today that the BBC will not be renewing his contract," he announced. "It is not a decision I have taken lightly. I have done so only after a very careful consideration of the facts and after personally meeting both Jeremy and Oisin Tymon."
Placing emphasis on Clarkson's legacy, Hall added that the BBC will be looking into a new host for "Top Gear" in 2016. "This will be a big challenge and there is no point in pretending otherwise," he said.
Inquiries are ongoing to establish where the threat came from, the police said.
A representative for the BBC told CNN: "We don't comment on security matters."