Pranksters have apologised for posting a missing poster declaring that a deadly black mamba snake was roaming free in north London. Black mambas, popularised in the Quentin Tarantino epic Kill Bill, are known for being lightning fast as well as being one of the most venomous snakes on the planet – with a bite that can kill a human in hours.

Posters warning of the snake escape appeared tacked to trees and on signposts in the King's Cross area of the city on 5 January. The snake, that was said to have been called "Rosie", sparked fears amongst residents, but today the posters were found to have been replaced with a new message.

The new posters, headlined "Snake Update", confirmed the elaborate hoax: "Dear residents, There is not a snake called 'Rosie' on the loose. The poster was a hoax. Sorry for any distress caused."

Despite suspicions being raised by the initial claim of the missing mamba the RSPCA were forced to launch an investigation whilst warning Londoners to be vigilant and to call police if they spotted "Rosie".

A spokeswoman for the RSPCA told the MailOnline: "We are pleased to hear that the reports of an escaped mamba are not real and no snakes or people are at risk. However we would like to remind people that pranks like this can potentially waste RSPCA time and money and cause worry and distress for many people."

The original poster told the public "If you see her DO NOT ATTEMPT TO HANDLE HER" and left a phone number. But after a number of attempts by officials to get in contact their calls remained unanswered – arousing suspicions of a hoax.

Black Mambas, named because of their inky-black tongues and throat, grow to around 2m long and are found in sub-Saharan Africa. They are predators that hunt hyraxes and bats, but are also hunted by the yellow mongoose.